This guide is for all players new and old, whether you're new to the game and want to learn the basics and get some tips or you're getting pretty good but just can't quite make to the end of the game no matter how hard you seem to try. This guide will be pretty subjective; I will probably not be giving specific details such as numerical data on item stats unless it's basic information amount the item - for example, I will tell you that 'The Pact' will give you two soul hearts, extra damage and a tears upgrade but not the numerical details on those stat increases - let's keep it simple!
Note: this guide assumes that you have purchased and installed The Wrath of the Lamb DLC - this DLC adds more items/floor types/characters/enemies etc. - if you haven't yet purchased it I would recommend it! It doubles the content of the game and is really worthwhile :)
I'll be updating this guide as much as I can so if you find it helpful don't forget to favourite it!
The Basics #1 - Controls, stats and consumable items
Here are the basics for the brand new players:
Move around with the standard WASD format and shoot with your arrow keys
Prefer a controller? I use an XBOX 360 controller by using Joy2Key[joytokey.net]! Try it out!
My guide on using Joy2Key can be found here
I can't stress enough that having the Isaac wiki[bindingofisaac.wikia.com] open while you're playing to research item specifics is essential to becoming good at this game. Find a new item? Search it on the wiki and find out exactly what it does and when it's best to use it!
Familiarize yourself with how Isaac shoots whilst moving - you will notice, for example, when moving right and shooting up, Isaac's tears will shoot at a 45 degree angle - in some situations using this technique can save you from taking a lot of damage, especially if you can run in and out from the cover of a rock!
Your basic stats are:
HP - your current health / maximum health
Damage - the amount of damage you deal to enemies per hit
Tears - this is your rate of fire i.e. how fast a tear fires after the previous one
Range - how far your tears go across the room
Speed - how fast you move
Your hidden stats are:
Shot speed - the rate at which tears travel once you have fired them
Luck - the likelihood of an item appearing when you finish a room - only Luck Up and Luck Down pills affect this stat. Due to a bug, having low/negative luck increases your chance at finding items/chests. Having positive luck increases your chance of shooting teeth instead of tears when you have the item 'Tough Love'. Positive luck also increases the chances of a payout from gambling.
Special stat - this stat is complex and worth researching on the wiki once you're an experienced player.
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Item pickups
Description
Red hearts - These are the lifeblood of your playthrough. Isaac will start with 3 hearts which will become empty as you take damage. Find hearts by defeating rooms, chests, champion versions of enemies and through certain items. You cannot have more than 12 red heart containers
Soul hearts - These hearts are sort of like 'armor' for your red hearts. If you have any, they will take priority over your red hearts when you take damage. Once they're gone, they're gone. You do not have soul heart containers as you do with red hearts and must find more if you wish to replenish them. You can have an infinite amount of soul hearts but they will not be visible on screen after you have 12 or more of any heart-type.
Eternal heart - Eternal hearts are very rare. They take damage before red hearts but are protected by soul hearts. If you pick one up, you can turn it into a red heart container by either completing the floor before losing it to taking damage or by finding another eternal heart.
Note if you have an eternal heart playing a Blood Donation Machine / IV Bag / Demon Judgement will take the eternal before it takes any other type of heart. Choose wisely.
Bombs - Bombs can be used to kill enemies, blow up rocks, open standard room doors, blow up slot machines/gamblers/blood banks and to find secret rooms. You can hurt yourself with bombs so be careful. My advice is to use bombs sparingly, as they are best used on tinted rocks and for finding secret rooms!
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Money - Money will come in the forms of pennies, nickels and dimes (special pickups of a quarter and a dollar are also findable special items though much rarer). Money can be used on gambling machines, Judgment Beggars and to purchase items from the shop.
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Pills - Pills come in a variety of colours during the game. The effects of the pill are unknown until the pill is taken (however, the pills effect can be known before using it after picking up the item 'PHD'). The pills effect can alter one of Isaac's stats either positively or negatively, such upgrading OR downgrading his speed, health, range, luck and rate of fire. Pills can also contain a one off poison effect to be used on enemies, switch around your bombs/keys (e.g. 5 bombs / 10 keys becomes 10 bombs / 5 keys) or teleport you to a random room on the map. It's important to note that during the run in which you find a pill, pills of that colour will always be the same throughout the rest of that run only. If a red pill gives you a health upgrade in one run, it can just as easily be a health downgrade in the next run, so be careful!
Note: Having the 'Lucky Foot' or 'PHD' items will remove negative pills from the playthrough in which you possess one of those items. Cain is a personal favourite of mine as a character as he starts the game with the Lucky Foot.
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Keys - Keys make your shots instantly kill enemies, including bosses, in one hit. No just kidding! You'd already guessed it; keys unlock locked doors and chests. Go figure. If you find a Golden Key, it will serve as a master key for every room/chest on that floor, but you will not be able to take it to the next floor. My advice is to use keys on golden chests sparingly, as they are much better used on treasure rooms and shops!
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Tarot Cards
Tarot cards have different effects depending on the type of card you pick up. There are a variety of Tarot Cards with effects ranging from temporary invincibility to instant teleportation to a boss room/item room/secret room/shop. Remember to keep the wiki open[bindingofisaac.wikia.com] so you can learn what each card does as you find it!
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Playing Cards - Playing cards are much more simple:
2 of Spades - Doubles your keys. If you have 0, you will get 2 keys.
2 of Clubs - Doubles your bombs. If you have 0, you will get 2 bombs.
2 of Diamonds - Doubles your money. If you have 0, you will get 2 pennies.
2 of Hearts - Doubles your hearts. If you have full health, this is useless. Best used when you are at 50% health.
The Joker - instantly teleports you to a Devil Room or Angel Room. Best used after defeating a boss and the Devil/Angel room fails to appear.
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Chests - Upon opening a chest, a random assortment of items may or may not come out. An active bomb that's ready to blow your face off or chase you down might also pop out. Be on your guard! If the chest is golden, it will require a key to open but has a chance of wielding much greater rewards for your risk!
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The Basics #2 - Gambling, Blood Donation and Beggars
The Shell Game
This guy, found only in the Arcade, will take 1 cent from you and in return you will have a 1 in 3 chance of receiving bombs, keys or more money from him. There is also a chance that he will drop 'Skatole', causing him to disappear forever. Picking up Skatole will stop most fly enemies from being able to damage you. Ones that can still damage you will be slowed down by Skatole.
Blood Donation Machines
Blood Donation Machines will take half a red heart (or soul heart if you only have just one half of a red heart left) in exchange for money. Blood Machines have a 1 in 15 chance of exploding and producing a Blood Bag or IV Bag upon doing so. Please see the 'My Advice' section for details on using the Blood Machine effectively. Floors after 'The Depths 2' will take a full heart.
Slot Machines / Fortune Tellers
These accept money in order for a chance to get an item. Slot Machines drop keys, bombs, pills, money and Pretty Flies and can also explode into a dollar bill giving you 99 cents. Fortune Tellers can drop spirit hearts, tarot/playing cards and trinkets and can explode into the 'Crystal Ball' item. Consult the wiki[bindingofisaac.wikia.com] for details on Pretty Flies and the Crystal Ball.
Beggar / Judgement
This guy can be found randomly on any floor or be summoned by using a Judgement tarot card. He will take one cent from you each time you bump into him and has a chance of giving you a pick-up in return (a key, bomb, heart, etc.). However, he also has the chance of giving you a special item, such as a Compass, Map, Nun's Habit, HP upgrade, etc. Upon giving you a special item, he will disappear. I find that Judgement pays out with a special item more often than not so if you have some cash to spare, throw it his way. It's a good idea to remain at 15 cents at the minimum if you have yet to see what the Shop of that floor has in store, though!
Blowing up Judgement increases the chance of a Devil Room appearing after a boss fight
Using a Judgement card to spawn a Judgement in a Devil/Curse/Angel room will lead to him paying out with an item from that pool
Devil Beggar / Demon Judgement
This guy also appears randomly or can be spawned from a Judgement card. However, this Judgement wants health instead of money. He will not drop any normal pick-ups except tarot/playing cards. However, he will drop an item at some point - the Devil Beggar will drop an item from the same pool as Devil/Curse/Angel rooms. You may find more often than not this guy makes you feel like a total idiot when you give him 6 of your 8 red hearts and he just sits there and gives you nothing. It's up to you if you want to play him, just make sure you don't go overboard if there's no quick means of refilling your lost health. A Nun's Habit + Yum Heart/Book of Revelations combo makes this guy a no-brainer play.
And finally: if you have no use for any of these guys/machines, blow them up with a bomb. They should all pay out with a pick-up item or two! However, Demon Judgement is the exception - he only pays you back with some enemy spiders - but it will increase your Devil Room chance by 35%!
Room types
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The Room
(you are tearing me apart, Lisa!) Description
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[/previewimg]Item Room / Treasure Room - Contains an item. You knew that!
[/previewimg]Boss Room - Contains a boss. Allows you to advance to the next floor upon defeating it.
[/previewimg] [/previewimg]Shop - The Shop is accessible by using a key and has various pickups for sale, such as red/soul hearts, keys, bombs and pills. There will also be a special item available from the shop such as the Treasure Map, Compass and Nun's Habit. Picking up the 'Steam Sale' after defeating Greed will make all items half price for the remainder of the playthrough.
[/previewimg] Arcade - The Arcade has a chance to appear if you enter an even numbered floor with 5 cents or more from the previous floor and costs 1 cent to enter. In there, you will find a Shell Game, a Blood Donation Machine and a Slot Machine or Fortune Teller.
[/previewimg] Curse Room - The Curse room will take half a heart from you in order to enter and leave. Inside the Curse Room, there will either be two Red Chests or, rarely, a free Devil Room or Angel Room item.
Some points about the curse room:
Red Chests have a chance of dropping:
any 4 of the Dead Cat/Guppy items (see Advice section for more on Guppy)
teleporting you to a Devil or Angel Room
spawning two enemy spiders
spawning two troll bombs or a super troll bomb that will chase you until it explodes
giving you three attack fly allies
pills
soul hearts
If you're flying by any means, you will not take damage on the way into the room
[/previewimg]Challenge / Mob Trap room - This room can only be entered if you have full health (or if your current red health and soul hearts make up how many heart containers you have). It will have a chest or an item upon entering. Opening the chest/picking up the item will unleash 3 waves of enemies which you must defeat one after the other in order to escape. You can avoid fighting the waves by using any teleport item.
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[/previewimg]Boss Challenge / Boss Trap room - The Boss Challenge room will offer you an item that is normally received upon defeating a boss in a normal boss room. However, you must fight two bosses in order to get out of this room alive. The bosses you fight are dependant on the floor you are currently on.
[/previewimg]Devil Room - The Devil Room has a chance to appear upon defeating a boss in any normal boss room. The chance decreases the more damage you take on that floor. The devil will offer you two items taken from a pool of specific items. However, in return, he'll want some of your health. Permanently. If you want that knife, or that book, you're gonna have to cough up some HP. See my strategy section for more.
The Devil Room can sometimes instead be a fight with the boss Krampus
The Devil Room cannot spawn on the first floor (basement/cellar) unless it is an XL floor
[/previewimg]Angel Room - Angel Rooms have a chance to appear if you have previously walked into a Devil Room and left without taking any deals on offer. They offer a different array of items (though some Devil Item equivalents) to the Devil Room and do not cost any health. Happy days!
[/previewimg] Sacrifice Room - Sacrifice rooms have a spike in the middle of the room which you can walk on. This will take one heart each time and each heart given will be a chance to get a chest in return. This room is practically useless and I avoid it every single time
[/previewimg] I Am Error room - Using a Telepills pill will have a 1 in 15 chance of taking you to the I Am Error room. This room will have a random mixture of items/pills/chests/pickups. You are forced to go to the next floor from this room unless you have another item which can teleport you (Teleport Remote, various tarot cards or you find another telepills in the room), so this room can be both a blessing and a curse.
[/previewimg]Library - The Library is accessible by using a key and has a 5% chance of appearing on a floor. It contains within it two random book items (though sometimes two of the same book).
Picking up a book during a playthrough gives a 25% chance of a library appearing on other floors for the remainder of the playthrough.
Secret Rooms
Secret Rooms
Secret rooms are, as you would guess, secret. They don't appear on the map until they are A) found or B) revealed to you by certain items.
Going into secret rooms will typically grant you money (usually 3 cents, 6 cents, or 9 cents; though you may get more if nickels/dimes are part of that make-up). They may also contain Slot Machines, Fortune Teller Machines, specific items or the miniboss Greed/Super Greed.
Secret rooms are found by placing bombs in the middle of the wall in a room adjacent to the secret room itself. Once the bomb explodes, a hole will be revealed and a mysterious tune will play. But what's the trick to finding the secret room?
Secrets rooms tend to be adjacent to at least 3 rooms - sometimes it's 4, sometimes it's 2 - but it's usually 3. On the picture below I have circled possible locations for the secret room
My advice is to wait until you have cleared out most or all of the floor, and then look for those horseshoe shaped gaps around rooms on the map. One of these will be your secret room! Some of the best items in the game can be found in those rooms (as well as a lot of money!) so be sure to check for them!
Super Secret Rooms
Super Secret Rooms have different rewards to the normal Secret Room. They can contain trinkets, fortune teller machines, tarot cards, eternal hearts or several red hearts! The secret room will most likely be adjacent to only one other room on the map.
Here is a map I have marked with X's showing likely locations for the super secret room:
Note: if you leave a secret room and then leave the adjacent room, you will have to use another bomb to enter the secret room again.
Items that can reveal secret rooms:
The Treasure Map (purchasable from shops or a chance drop from a Judgement Beggar). Will only reveal normal secret rooms.
The X-Ray Goggles - when you walk into a room wearing these, the secret room hole will already be there and you can walk through it as much as you wish. Will open secret and super secret rooms.
Spelunker Hat - will reveal the locations of secret rooms when you walk into the adjacent room, but you will need to bomb your way into it each time to get in there. Will reveal both types of secret room.
'The World' tarot card - reveals the whole map to you, including the normal secret room
The Crystal Ball - reveals the map including the normal secret room and also gives you either a soul heart or tarot card
Tips & Tricks #1
Play as Cain
Cain, in my opinion is the first character you should unlock and play with in order to progress through the 'Complete game X times' achievements (which unlock more items) as he has a higher chance of success with gambling and cannot get negative pill effects.
Once you are more comfortable with your Isaac skill, Judas is great practice for high damage/low HP playthroughs.
Tinted Rocks
Now and then you will catch in the corner of your eye a rock that is tinted blue. Use your bombs on them! Blowing them up can give you soul hearts, keys, bombs and even a damage upgrade in the form of the 'Small Rock'!
Blood Donation Machine
As said before, this has a 1 in 15 chance of exploding into one of two items: the Blood Bag or the IV Bag. The IV Bag will act a portable donation machine, taking hearts for money. The Blood Bag is an HP and speed upgrade combined (and also refills 5 HP if you've taken some damage before you picked it up). If you find an arcade/blood donation machine on a floor, be mindful of any red hearts on the floor. Stay on the floor longer than you would normally in order to play this machine, that extra HP will make a lot of difference, especially if you're taking deals with the devil.
The Nun's Habit
The Nun's Habit is an amazing item found in the Shop. When hit, you will recharge 3 bars of your 6-bar active item. With the right items, this allows you to become pretty much unstoppable. The 'Yum Heart', which heals one red heart per-use, will recharge to full every time you take 2 hits (i.e. one heart), so every time you lose a heart, you can immediately get it back. If you come across this combination abuse it for infinite plays on the Blood Donation Machine until it pays out with a Blood Bag or IV Bag.
Notes:
After the IV bag has been picked up once all future machines will pay out with a Blood Bag.
Maggie already starts with the Yum Heart. Obtaining the Nun's Habit as Maggie is great as the Blood Bag will provide her with even more heart containers and the extra speed Maggie desperately needs as she starts with the lowest speed of any character.
You can do the same thing as above using the Book of Revelations or The Nail but instead you will gain soul hearts rather than red hearts - this is useful in the early game to stack up on soul hearts for the late game.
+ The Blood Penny + Donation Machine combo
The Bloody Penny is a trinket that appears quite late on in the game (by defeating The Cathedral with Samson), so you'll probably be quite the Isaac player by that point! But just so you know, the bloody penny will give you a chance to get red hearts every time you pick up a penny. The Blood Bank gives out pennies for hearts. See the cycle? You lose health, it gives you money, the money gives you health. Abuse this like you would abuse the Habit to get as much as you can out of the Blood Machines for the max amount of HP upgrades possible!
Deals with the devil
Deals with the devil look pretty risky. You're losing a lot of health for some items and it may not seem like a good trade. Early/new players tend to think that the best thing to stack up on is HP for the maximum chance at winning. It's not. The best thing to stack up on by far is damage. My general rule while I play is that if taking a deal with the devil will leave me with at least 2 red heart containers while giving me extra damage, I will definitely take it. Damage makes all the difference. The following items are my favourite devil room items:
The Pact - gives you more damage and increases your rate of fire while also giving you 2 soul hearts
Brimstone - this also gives you infinite range via a charged laser attack that also pierces through enemies and rocks. Possibly one of the best items in the game.
The Mark - gives you damage, speed and a soul heart.
Common Cold - gives your shots a chance to poison enemies
Spirit of the Night - while it doesn't give you damage, it gives you the ability to fly and gives you spectral tears, meaning you can now shoot through rocks/obstacles. This is an amazing defensive item and I'd recommend taking it any time it shows up.
Blue Baby + Book of Shadows/Polaroid + Devil Room
Blue Baby/??? has the unique ability to steal items from the Devil Room under certain circumstances. Blue Baby is not able under any circumstances to get red hearts and must subsist solely on soul hearts - getting any HP upgrade will only give you a soul heart. This means that if Blue Baby has a shield he is able to take items from Devil Rooms without losing any soul hearts. This can be accomplished by either using the Book of Shadows while in the Devil Room or hurting yourself with a bomb in a Devil Room whilst in possession of The Polaroid
Although I say Blue Baby has the unique ability to do this it is possible to do this with other characters by either giving up all your red hearts while retaining soul hearts (Devil Room) or using Guppy's Paw so that your character is only subsisting on soul hearts as Blue Baby does.
Becoming Guppy
It is possible to turn into Isaac's cat Guppy with the acquisition of specific items in the game. Guppy has the ability to fly and can spawn flies that attack enemies whenever you successfully hit an enemy. You must have at least once picked up any 3 of these 4 items during one playthrough:
Guppy's Head - Spawns flies around you that attack enemies. Recharges every room.
Guppy's Paw - each usage turns one red heart permanently into three soul hearts.
Guppy's Tail - increases the chance of golden chests appearing throughout your playthrough.
Dead Cat - removes all of your red hearts except for one and allows you to die 9 times. Each time you die you will only respawn with one red heart container.
Tips & Tricks #2
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Tip
The D6
The D6 is unlocked by defeating Mom's Heart/It Lives with ???/Blue Baby - once it is unlocked, Isaac will always start with this item. (If you are having a hard time with this, try to find the Ankh from a secret room and kill yourself just before fighting Mom's Heart. You will respawn as ???/Blue Baby and will unlock the D6 if you win the fight)[/b]
The D6 has the ability to reroll any special item, passive or active, into another item from the same pool (i.e. Devil Room items will reroll into another random Devil Room item, Shop item into another Shop item etc.). This can be used to increase your chances of getting certain items that you want/need to complete your run or goal.
What you should reroll if you don't like what you see:
Item rooms
Shop items
Secret room items
Boss room items
Boss Trap / Mob Trap room items
Items that drop from Judgement or Demon Judgement
Devil Room items
Angel Room items
Curse Room items
Items that drop from golden or red chests
Books in the library
Tip
Picking up active items that you see throughout your run will take them out of the pool, preventing them from appearing again later in the game. This also works in the case of D6 rerolls. If you pick up, say, Anarchist's Cookbook, it will not appear again throughout that run. This mechanic can be used to gain an advantage e.g. in the library.
Rerolling the Libray into a double-item room
If you are on a floor with a library, you may go into that library and take the two current books out of the pool by picking them up and putting them back down. Then reroll them. They will turn into another set (or 2 of the same book) of books. Recharge your D6 and repeat until all the books are out of the pool and the reroll will draw from another item pool, essentially making the library a double item room. This strategy works great with a combination of the D6 + Battery/9 volt and also the Nun's Habit as getting hit will recharge your D6 even faster.
Getting an extra free Devil Room item
When you walk into a devil room, you can reroll the items as long as your D6 is charged. If you don't like the items you first see, reroll them. If you see an active item that would benefit you in some way, for example, picking up Guppy's Paw or Guppy's Head to increase your chance of becoming Guppy, you can pick up that item, put it back down and reroll it into another item which you can then take for free. The item will roll into another (but this time free!) Devil Room item, which may be another Guppy Item, or a great passive like Brimstone, Spirit of the Night or Mom's Knife!
Items that won't reroll
Some items in the game are from a separate pool all by themselves and they won't reroll into another item (with two exceptions). Those items are:
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Steven
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Little Steve
Little Gish
Little C.H.A.D.
Cube of Meat
A Pony - can be rerolled once it has been picked up and put back down
White Pony - can be rerolled once it has been picked up and put back down
Tips & Tricks #3
Bridge the gap!
If you see a situation like the picture above and you can't fly (or you don't have the magnet!) you can still get to that item! If there is a rock parallel to the 'island' that the item is on, you can place a bomb behind the rock to blow the rock into the gap in order to bridge it. The rock must been blown in the direction of the gap however or it will not work!
Fight the same boss twice for another item!
If you have the tarot card 'Wheel of Fortune', you can use it after defeating a boss (whilst still in the boss room) and play it there. If it eventually spawns an enemy fly, leave the room and go back in without killing the fly. The game will register the boss fight as if you escaped and you will fight it again! You will then be able to get another item from defeating the boss again if you wish.
Miniboss Rooms and Shop Rooms
After Caves 2 and beyond, there is a chance that Greed or Super Greed will be in the Shop rather than purchasable items. However, if you fight Greed in a secret room or you fight any other miniboss (any of the 7 Sins) on the floor, Greed will defintely not be in the Shop.
The Mr Mega Glitch
If you place a bomb and exit + re-enter the room before it explodes, it will have an increased blast radius similar to that of a Mr Mega or Mr Boom explosion. This allows you to blow up more rocks or find the secret room whilst also blowing up tinted rocks, bridging gaps or making gaps to collect trapped items.
Judgement item pool
Spawn a Judgement via a tarot card in a Curse, Angel or Devil room to have him pay out with an item from those pools!
Killing any Judgement or Shell Game will increase the chance of a Devil Room appearance by 35%
[/previewimg]Bad Trip's can be amazing
The pill 'Bad Trip' will turn into a Full Health pill when you are down to just one heart. If you're playing as ???/Blue Baby you must be down to half a soul heart instead; using it at one heart will kill you.
Brimsnapping
This is another bug like the Mr Mega Glitch but it makes you insanely overpowered. When firing Brimstone, repeatedly pressing the direction you're firing in after the initial shot will cause multiple bursts of brimstone to fire out and deal multiples of damage - for example, if you fire brimstone to the left and then press the left arrow key three times as fast as you can, you will deal four times the amount of damage.
Tips & Tricks #4
Getting a Devil/Angel room after the Mom fight
If you can, take any of the following items into the Mom fight:
Teleport Remote
Telepills
Stars Tarot Card
Hermit Tarot Card
Moon Tarot Card
The Fool Tarot Card
After you defeat Mom, use any of those items to teleport out of the room. When you go back in, you might find that a Devil or Angel room is now accessible.
Using Teleport Remote for free Devil room items
If you have enough soul hearts for a soul heart deal with devil, using the Teleport Remote as you run into the item can get you the item for free if you time it right.
Things to avoid
Misleading Devil/Angel Room after Mom's Heart/It Lives!
After defeating Mom's Heart/It Lives! a Devil or Angel room can sometimes appear. Neither will ever give you item. These rooms will only have a trap door that will lead you to Sheol. If you are planning to go the Cathedral (for achievements etc.) you can find yourself disappointed when you go in there and end up in Sheol, so be careful.
Using Telepills on 'The Chest'
Using Telepills on 'The Chest'[/url] can send you to an I Am Error room. This room can screw up your run if you find it on The Chest[/url] as there are no trapdoors or normal doors to leave the room. If you do not have the Teleport Remote you will not be able to leave the room and have to quit and start from the beginning. [watch video]
Bugged Achievements
The end-game achievements 'Defeat Sheol/The Chest with X' are bugged as of v1.48. Make sure you check the achievements wiki[bindingofisaac.wikia.com] to make sure you pick the right character for the right achievement.
Extra: Shot speed upgrades explained
Shot speed upgrades
One of the hidden stats, 'shot speed', increases how fast your tears travel across a room. This may seem like an advantage at first but in fact it can be a huge disadvantage. This is because shot speed also increases the amount of knockback an enemy suffers when they are hit. This can make them extremely unpredictable and make them run at you in ways that they wouldn't without the shot speed upgrades. I would recommend avoiding the following items for that reason:
Magic 8-ball - Increases shot speed by 16% and gives you a random tarot card. This item displays the 'tears up!' message upon pickup but has no actual effect on rate of fire, only shot speed. Avoid it unless you badly need a tarot card.
Toothpicks - increases shot speed by 16%. Despite it turning your tears red (which usually indicates a damage increase), it has no effect whatsoever on your damage. Not worth picking up.
Cat O' Nine Tails - increases shot speed by 23% - this item is the worst of all. It slows items like Brimstone and Technology 2 and also makes Lump of Coal much less effective. Avoid this item completely. If it appears after defeating a boss, just leave it.
Shot speed upgrades worth picking up:
Stem Cells - increases shot speed by 16% but also gives you one HP-up and heals 1 and a half hearts.
Speed Ball - this item is worth picking up if you are playing as Maggie and you've yet to pick up a speed upgrade. Increases shot speed by 20%.
Lump of Coal synergy
A Lump of Coal - Rewarded to you for beating Krampus in a Devil Room, A Lump of Coal increases the damage of your tears for every second they are on screen before they hit an enemy. Shot speeds therefore make the A Lump of Coal less effective.
A Lump of Coal will increase the damage of Brimstone, Technology (1 and 2) by +2.
Extra: No damage / 'X Boy' Achievement tips
Complete X Floor without taking any damage
These achievements are the hardest to get in my opinion and are down to both luck of the draw on items and the skill of using those items. The achievement will unlock when, having taken absolutely no damage, you defeat the boss (or second boss of an XL floor) of the second floor of each series (Basement 2, Caves 2, etc.) - you do not need to go down to the next floor to obtain it.
My advice is to focus on these achievements solely during the runs that you try to get them. Don't be concerned about winning the run as a whole. With such a route, you can go all out on aggressive devil deals and get the maximum damage possible (since hey, you don't need HP since you're aiming not to get hit at all, right?). The combination that I used to get these achievements were:
Brimstone - Brimstone gives you high damage which pierces through enemies and obstacles with infinite range.
Lord of the Pit - LOTP gives you the ability to fly as well as a speed upgrade, allowing you to very effectively dodge enemies and bosses. Great when combined with Brimstone.
Book of Shadows - gives you about 10 seconds of invincibility when used - great for rooms where damage is nearly unavoidable or if you get yourself trapped in a tight spot!
Other items that will seriously help you out are:
Mom's Bra - freezes enemies temporarily, giving you a good shot at taking them out
Mom's Pad - enemies will back away from you for 5 seconds - great for rooms where you get rushed by flies or a tonne of ground enemies
Necronomicon - deals massive damage to all enemies in a room - great for rooms with lots of flies
Unicorn Horn - makes you invincible and do damage to enemies you run into for about 5 seconds
Gamekid - same as the Unicorn Horn and Mom's Pad (though also heals you if you've lost hp)
Supplementary items:
The Battery - recharges one bar of your space bar item every 15 seconds in a room with enemies (up to 3 charges)
9 Volt - makes your space bar item charge faster.
If you get any combination of these items just do your best to use them effectively and get those achievements!
You can take damage on the floor sets below/after the one you're trying to get. If you are looking to get 'Dark Boy' (no damage on the Depths 1 and 2) then get high damage/flying devil items if they come up BEFORE the Depths (Basement 1 and 2, Caves 1 and 2). Do not take devil deals on the first floor of the set you're trying to get the achievement with. If you're trying to get Dark Boy and take a devil deal on Depths 1, it will count as damage.
Extra: How to unlock the other characters
Character
How to unlock
Cain - unlock Cain by having 55 coins or more at some point during a playthrough. You must have 55 coins at once, having all the coins during your run add up to 55 will not count. My advice for unlocking Cain is simply to avoid going to Shops during your run until Caves 2 and beyond. Once you have reached Caves 2, the Shop will sometimes contain the miniboss 'Greed' or 'Super Greed' who may drop a tonne of cash upon their defeat. Another good idea is to frequently look for secrets rooms as they often contain money (more on secret rooms in another section)
Maggie - unlock Maggie by having 7 or more heart containers in one playthrough. Again you must have 7 or more at one time. My advice for getting Maggie is during your run refuse deals with the devil and play Blood Banks for a chance at some extra HP! (more on that in another section!)
Judas - unlock Judas by defeating the boss 'Mom's Heart' - this boss is unlocked after completing the game for the first time by defeating Mom in The Depths / Necropolis 2.
Samson - unlock Samson by defeating Mom but having passed up two Item Rooms during your playthrough. This one can be difficult for new players as you will be relying on items to get you through. Tackle this unlock when you are a bit more experienced!
Eve - unlock Eve by making two deals with the devil during one playthrough. Devil Rooms are rooms that have a chance to appear in the Boss Room after the boss is defeated. The less red-heart damage you have taken on that floor, the bigger the chance. If you're really set on unlocking Eve, take a second deal with the devil even if it will kill you. Eve will still unlock.
??? / Blue Baby - unlock ??? by defeating the boss 'It Lives' - this is equivalent to finishing the game 10 times as 'It Lives' is unlocked after defeating the game 9 times. ??? will most likely be the last character you unlock - trust me, there's a good reason for that.
