Tainted Keeper starts with (and has a maximum of) 2 coin hearts and 1 Bomb. Tainted Keeper shares the same mechanics with the regular Keeper, including recovering one coin heart upon picking up a coin, as well as converting any heart pickups to blue flies. Picking up a coin to restore a heart does not add a coin to his coin counter. Tainted Keeper shoots four tears at a time, similar to the item Mutant Spider. Whenever an enemy is defeated, a random coin is dropped that will vanish quickly. Most items encountered when playing as Tainted Keeper must first be paid for with coins, including Deals with the Devil, Angel Room, Boss Room items, and Treasure Room items.
In the standard game mode, Shops are different and much better for Tainted Keeper. They do not require a Key and generally have increased stock available. At max level, they have eight items/pickups for sale, of which there will always be at least one Shop item, one Boss Room item, and two Treasure Room items. The other four terminals in the shop can be keys, bombs, cards, pills, trinkets (which will be sold for 5 cents), or more Shop/Treasure Room items.
This shop can rarely be replaced by a better (or worse) variant: The better variant has 2-6 more shopkeepers, Urns scattered about, two Lucky Pennies, and one more random item/pickup for sale. The worse variant has only one random sale terminal, one Shopkeeper, some Poop, and a Fly.
Enemies spawned after entering the room (i.e. spawned by another enemy or spawned on later waves in Challenge Rooms) don't have a guaranteed coin drop.
Spawned enemies will stop dropping coins after fights go on long enough such as with Boss Rush.
Champion enemies and Mini-Bosses drop 2 coins on death.
Bosses drop several coins.
If the boss comprises multiple enemies (e.g. Gurglings), each of them drops fewer coins.
Most degraded bosses drop 3 coins, exceptions such as The Cage and Monstro II have regular boss coin drops.
Coins dropped by bosses stay on the floor longer before disappearing.
Boss Rush items must still be paid for, and doing so will start the event.
Because Tainted Keeper has to pay for all items, taking devil deals is often more powerful than taking Angel items. This is because taking one devil deal item will not despawn the other items, but only one item can be taken from an Angel room.
All items that normally cost two hearts in a Devil Deal
Sticky Nickels are able to spawn as a result of killing enemies, effectively making them impossible to collect (aside from having an accompanying explosion to break it free after spawning, and being mindful enough to collect it in time), as it would have already disappeared by the time a bomb detonated to pick it up. Remote Detonator would help, but it could end up in self-damage as the explosion would have to be extremely quick.
Coin drops from enemies are generated when a room is first generated. If an enemy that begins in the room drops a nickel, dime, or penny variant, it will drop the same coin if you leave and re-enter the room. This makes items such as Mercurius, Ventricle Razor and Door Stop much more useful, as they allow the player to easily leave and re-enter the desired room, allowing the player to easily generate money to fuel the run. This will, however, make the enemies start dropping less and less money each time you kill them, eventually not dropping anything.
In Co-Op, all players will need to use money to purchase items if Tainted Keeper is in the game, but enemies will also drop money regardless of who killed them.
With this in mind, having the Blessed Penny can earn a huge amount of Soul Hearts for the players who can use them quickly.
This can be used to get Devil Deal items without losing health for all players.
Tainted Keeper can utilize Sacrifice Rooms much more reliably and efficiently than other characters, because monsters reliably generate health. This can be done by leaving regular coin drops on the floor to go pick up, or alternating stepping on the sacrifice spikes with clearing a monster room. The latter is reliable to produce coins but risky because you're always entering an unknown monster room with one health, but can be used with restarts to start a run with one or two angel room items. Keep in mind that Tainted Keeper has to pay for items in Angel Rooms that you may get at the 6th sacrifice, though the item drop you may get at the 7th sacrifice will be free.
Having a good speed stat may be very beneficial, in order to pick up coins before they disappear.
Golden Pennies are able to spawn as a result of killing enemies. It still despawns like a normal coin unless picked up, in which case, any subsequent spawns will not disappear.
Pressing reward plates is more worthwhile as enemies spawned by buttons reward extra coins.
After entering Curse Rooms, try to exit the room immediately.
If there are enemies in the room, you will not be able to leave, but the dropped coins will ensure you have health to exit safely.
If there are no enemies, you'll exit the room while invincibility frames are active and will not lose your second coin heart.
It is also recommended to save teleport cards/pills/items for entering curse rooms, so you may safely leave regardless.
Interactions[ | ]
Sack Head: Similarly to how the chance for dimes and nickels to appear are determined by the seed, sacks are as well: rerolling the enemies in a room with D7 will result in them dropping sacks again if they had the first time, with the same exact contents inside the sack every time.
Hematemesis pill makes Tainted Keeper spawn coins instead.
2 of Diamonds will also heal Tainted Keeper, at the cost of 1 coin after doubling your coins.
Favored Items[ | ]
Birthright strongly attracts coins dropped by defeating enemies to Tainted Keeper, doesn't affect other coins.
Blood Rights effectively allows for free damage as long as you can get to a dropped coin (this, however, will result in less coins collected overall, since pennies dropped from faraway enemies will be impossible to reach before they disappear).
The Boomerang/Jaw Bone allow for Tainted Keeper to retrieve dropped coins that are otherwise inaccessible, such as ones over a pit or a gap.
Brittle Bones: Picking this item up will give a one-time +0.5 tears up ( +0.4 fire rate) and 24 Blue Flies without removing any health. This bonus is retained even if the item is later lost or rerolled.
Most Penny Trinkets are powerful from the sheer amount of coins Tainted Keeper is able to earn.
Burnt Penny and Flat Penny allow Tainted Keeper to obtain large amounts of keys and bombs.
Burnt Penny in particular is especially powerful; in a room with enough enemies, it is possible to gain infinite money and bombs by killing most enemies in the room, then bombing your way out of the room to reset it.
Counterfeit Penny can give an additional coin for each one you pick up, helping you gather money much more quickly and allowing you to afford more items.
Cursed Penny allows Tainted Keeper to farm infinite money. Killing an enemy drops a coin, which will teleport him to a different room and reset the current one.
Rotten Penny allows Tainted Keeper to amass a large amount of blue flies.
Bloody Penny and Blessed Penny act as somewhat weaker versions of the Rotten Penny, due to Tainted Keeper replacing all heart drops with flies.
D7 Because coin drops are determined by the seed, the D7 can be used to reset a room with a valuable coin to get it twice. Can additionally be used in Shops and Secret Rooms to refight Greed and Super Greed, allowing for large coin generation.
Deep Pockets guarantees 1-3 coins when clearing rooms if they would otherwise have no drops, and increases max number of coins to 999.
Devil's Crown's downside is heavily mitigated, as you would have had to pay for the item regardless of if it is a devil deal. That said, deals that would normally be 2 hearts still cost 30 cents, and buying the devil items will still lock you out of getting Angel Rooms.
Door Stop effectively allows for infinite money with enough patience. Tainted Keeper can leave 1 monster alive in a room, leave, and re-enter to collect even more coins from killing enemies. The chance of them dropping another coin lessens and lessens, so it could be ineffective.
Fruit Cake can have a consistently positive effect overall, as you gain the Eye of Greed, and Head of the Keeper chance of effects to your tears, as well as the overall other tear modifiers, on top of beginning with the 4 tears per shot, instead of 3, further increasing the chances of multiple effects, allowing you to have a much higher chance of generating coins.
Golden Razor is very useful for end-game bosses since Tainted Keeper usually has a large stock of coins with few places to spend them.
Greed's Gullet works very well to address Tainted Keeper's low health, able to grant up to 4 additional coin hearts, and up to 12 additional containers if you also have Deep Pockets. Keep in mind that you do have to buy most of your things, and that lowering your coins below each threshold will also remove a coin heart.
Humbleing Bundle has a chance to double the coins dropped from killing enemies.
Isaac's Heart makes Tainted Keeper's body invulnerable and grants contact damage, making it much easier to collect coins. It also makes strong synergy with Midas' Touch.
Keeper's Sack gives stat upgrades with every purchase, which is available much more often with Tainted Keeper than with other characters.
Magic Fingers can be used to kill every enemy in the room, and is sustainable with the coins they drop. The item is especially useful with high damage, or on later floors that do not have shops to spend money in.
Meat Cleaver: Multiplied enemies will always drop coins
Member Card/The Stairway add additional shops for Tainted Keeper to purchase items and pickups in.
Missing Page 2 essentially activates every time Tainted Keeper takes damage.
Money = Power and Midas' Touch can combine with the large number of coin drops in general to increase Tainted Keeper's damage steadily, even more so with Deep Pockets.
Portable Slot can be used to generate coins to heal Tainted Keeper during extended fights
Satanic Bible won't provide Black Hearts, since Tainted Keeper can't hold them, but it will provide a few flies and change boss items to more powerful Devil Room items at no real downside, since Tainted Keeper must purchase his boss items anyway.
Steam Sale reduces prices of all items, even outside the shop.
Sack Head: The pennies dropped from killing enemies have a chance to be sacks instead. The sacks do not flash and disappear. However, this might also mean that killing an enemy won't give you a coin when you really need one.
Virgo and Celtic Cross has a chance of allowing Tainted Keeper to safely regain lost health and collect coins after getting hit; this is very good for killing large groups of enemies.
Voodoo Head adds a penny to all Curse Rooms, letting Tainted Keeper regain lost health and safely exit the room.
Fanny Pack can be used to break the game in a room with many enemies by taking damage and killing enemies to heal back the lost health. Fanny Pack may provide bombs when you take damage, allowing you to continuously bomb out of the room and re-enter.
Mother's Kiss will allow Tainted Keeper to have 3 Coin hearts, which is the only method other than Greed's Gullet to harbor more than 2 Coin hearts. If the trinket is dropped, the extra Coin heart will disappear. Gulping it will add a permanent Coin Heart.
Like Keeper, Tainted Keeper can technically have unlimited coin hearts by swallowing many copies of Mother's Kiss.
Sigil of Baphomet can be used to let Tainted Keeper grab coins without risk of taking contact damage after killing an enemy.
Key Bum's downsides are much less noticeable, as Tainted Keeper doesn't heavily rely on Treasure Rooms and can enter shops without spending a key.
Situational Items[ | ]
HP Up items (Apart from Greed's Gullet and Mother's Kiss) don't do anything. Unlike regular Keeper, Tainted Keeper can never have 3 hearts. Only take them if your health has been reduced in any way (such as by taking Dead Cat).
While Bum Friend or Bumbo would be items normal Keeper would want to stay away from, Tainted Keeper could potentially benefit from these items considering the large amount of coins he is able to produce.
Butt Penny is useful for pushing away and poisoning enemies, but can cause other coins to be pushed away and time out.
Charm of the Vampire: Charm of the Vampire is redundant, as there is already consistent healing from enemy coin drops.
Dataminer can achieve integer underflow easily. This is when the tear rate becomes negative, which then causes tears to shoot up to max 120 tears per second. Tainted Keeper only needs 2 tears down procs to get to -0.01 tears as he begins with a fire-rate just below 1.00.
Be advised taking any tears or fire-rate ups after this including with Dataminer will reset the tears to an extremely low rate (e.g. 0.09).
Pageant Boy is generally a bad item, as it usually pays out with 7 cents and costs 15. However, if it is on sale, it is almost always worth picking up, as it will always at least pay for itself, and has the opportunity to net a profit if a more valuable coin spawns such as a Nickel or Dime.
20/20: Decreases damage to 80%, but increases the default tear stat, making it 2.73 without other items and effects. This allows him to double his damage output with tears. Decreases the spread of tears fired, making it easier to hit a single enemy with more tears.
As Tainted Keeper can reach 5.0 tear rate cap, this item becomes less effective damage-wise by the time Tainted Keeper gets to 3.75 tear rate without 20/20 and becomes disfavored after that, overally making him output less damage per second with tears.
Champion Belt and Purple Heart can be beneficial, as champions drop 2 coins, with drawback of fighting more champions.
D20: Can reroll coins dropped by Tainted Keeper into other pickups, but they will still disappear if not picked up quickly.
Disfavored Items[ | ]
Currently Damocles does not work with Tainted Keeper, as every item needs to be purchased.
Items that decrease Tainted Keeper's size like Mini Mush and Pluto should be avoided, as the smaller hitbox makes it harder to collect coins dropped by enemies.
Black Hole, Lodestone, and Ocular Rift can make it difficult for Tainted Keeper to collect coins as they will be pulled or pushed away.
E. Coli/Flush!: Enemies that are turned into poop don’t drop coins.
Experimental Treatment: Risky for Tainted Keeper in two ways; It has a chance to either set his health down to 1 coin heart or cut his starting tear rate in half.
Items that deal damage to every enemy in a room, such as Toxic Shock and Butt Bombs, can make it difficult for Tainted Keeper to collect coins as they will spawn rapidly across the entire room as multiple enemies die at once.
Heartbreak: Immediately turns the second coin heart into a broken coin heart, and the next hit will kill Tainted Keeper.
Mutant Spider: Tainted Keeper will now shoot six tears with x0.42 tears modifier. This reduces his damage output per second by ~36%.
The Inner Eye: Tainted Keeper will now shoot five tears with x0.51 tears modifier. This reduces his damage output per second by ~38%.
III - The Empress? will not increase health past 2 coins, and will reduce it to 1 at the end of its duration.
Uranus: Frozen enemies DO drop coins but multi-stage monsters such as Big Spiders or Dank Squirts will not split into smaller enemies, reducing total coin output. In addition, the collision of frozen enemies may block coin pickup.
Tainted Keeper's locked character icon, depicting a shop’s door.
Trivia[ | ]
Tainted Keeper having two coins on his eyes is possibly a reference to Charon's Obol, a tradition in northern Mediterranean cultures, particularly Greek and Roman cultures, where one would place a pair of coins on the deceased's eyes to pay Charon, the ferryman of the river Styx, for the trip across, but also to pay for a return trip from the world of the dead if one was expected. This is further supported by the fact The Lost, whose starting coin is also suspected to be a reference to Charon's Obol, only has one coin and is depicted as a spirit, while Keeper has two and is depicted as a corpse, supposing he paid to bring his body back across the river Styx.
Like his non-tainted counterpart, Tainted Keeper's starting health is listed as "II" on the character selection screen, despite having no red hearts. This is unique among such characters, whose health is usually listed as "-I" or "?".
Through his abilities and appearance, Tainted Keeper is the equivalent of Super Greed as Keeper is to Greed.
The achievement for unlocking Tainted Keeper is "The Miser", a possible title for the character.
A miser is someone who obsessively hoards money and refuses to spend it, the former of which fits Tainted Keeper's penny-pinching playstyle.
Defeating Ultra Greedier as Tainted Keeper unlocks XII - The Hanged Man?, most elements associated with Greed in Isaac are shown to be hung or having nooses.
When reversed, The hanged man represents selfishness and stubbornness, this can be read as Tainted Keeper treating all item rooms as shops and his attributes being "upgrades" from Store Key, Wooden Nickel, and triple shot, but deepening his disadvantages like lower health ceiling, lower tear rate cap, and applying Keeper's bargain to all item pedestals.
Keeper. Tainted Keeper is unlocked by reaching 
Home and using the 
Red Key, 
Cracked Key, or 
Soul of Cain to access a special room in one of the walls while playing as Keeper.
Bomb. Tainted Keeper shares the same mechanics with the regular Keeper, including recovering one coin heart upon picking up a coin, as well as converting any heart pickups to blue flies. Picking up a coin to restore a heart does not add a coin to his coin counter. Tainted Keeper shoots four tears at a time, similar to the item 
Mutant Spider. Whenever an enemy is defeated, a random coin is dropped that will vanish quickly. Most items encountered when playing as Tainted Keeper must first be paid for with coins, including Deals with the Devil, 
Angel Room, 
Boss Room items, and 
Treasure Room items.
Key and generally have increased stock available. At max level, they have eight items/pickups for sale, of which there will always be at least one Shop item, one Boss Room item, and two Treasure Room items. The other four terminals in the shop can be keys, bombs, cards, pills, trinkets (which will be sold for 5 cents), or more Shop/Treasure Room items.
Sticky Nickels are able to spawn as a result of killing enemies, effectively making them impossible to collect (aside from having an accompanying explosion to break it free after spawning, and being mindful enough to collect it in time), as it would have already disappeared by the time a bomb detonated to pick it up. 
Remote Detonator would help, but it could end up in self-damage as the explosion would have to be extremely quick.
Sacrifice Rooms much more reliably and efficiently than other characters, because monsters reliably generate health. This can be done by leaving regular coin drops on the floor to go pick up, or alternating stepping on the sacrifice spikes with clearing a monster room. The latter is reliable to produce coins but risky because you're always entering an unknown monster room with one health, but can be used with restarts to start a run with one or two angel room items. Keep in mind that Tainted Keeper has to pay for items in Angel Rooms that you may get at the 6th sacrifice, though the item drop you may get at the 7th sacrifice will be free.
Golden Pennies are able to spawn as a result of killing enemies. It still despawns like a normal coin unless picked up, in which case, any subsequent spawns will not disappear.
Keeper Unlocks 
Tainted Keeper Unlocks 
Characters 
The Binding of Isaac: Rebirth
