Tainted Fiend is an unlockable character in Fiend Folio, a mod for The Binding of Isaac.

Malice (consumable slot)

Constantly leaves slowing black creep behind him.

Enemies killed with Malice have a 20% chance of dropping a Half Black Heart.

When the Malice effect ends, Tainted Fiend breaks down into several minions. A minion is spawned for every Half Black Heart Tainted Fiend has, with a minimum of 2 spawned. He can reform back to Tainted Fiend by using Malice again.

Minions can be controlled just like Tainted Fiend. They share his stats and items, and have smaller hitboxes.

The damage stat is decreased when split in minions, and it depends on the amount of minions: (DamageStat × 0.8 + (DamageStat × 2.25 - DamageStat × 0.8)) / AmountOfMinions).

Each minion dies in one hit and removes one Half Black Heart from Tainted Fiend's health bar. If all of them die, however, Tainted Fiend dies as well, despite the health bar not being empty.

On the other hand, Tainted Fiend cannot die from heart loss when split. When at half a heart left, taking damage will kill a minion without deducting health.

The damage stat is calculated when the split happens. Minions dying will not increase damage for the rest of them.

If a minion takes damage, all of them gain short-lasting invincibility frames.

Placing a bomb while spit will place a tiny bomb from each minion. The bombs do damage equal to BombDamage / AmountOfMinions * ((1 + AmountOfMinions ^ 0.33) / 12).

Minions can pick up Spicy Keys without taking damage.

Any coin dropped has a 5% chance of being converted into a Cursed Penny.

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Health
Tainted Fiend can only have Black Hearts. Any HP up item that would grant a different type of heart will give a Black Heart instead.

The maximum amount of hearts Tainted Fiend can have is limited to 6.

Soul Hearts, Eternal Hearts, and Gold Hearts spawns will always be converted into Black Hearts.

Half Soul Hearts spawns will always be converted into Half Black Hearts.

Blended Hearts spawns will always be converted into Blended Black Hearts.

Bone Hearts have a 20% chance of being converted into Black Hearts.

Any other type of heart has a 33% chance of being converted into a Black Heart (or Half Black Heart if it's a Half Heart), with the chance going up to 66% with 13 luck.

Heart conversion (except for Soul Hearts and Blended Hearts) will not happen inside of Super Secret Rooms. Other types of hearts, however, cannot be picked up.

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Birthright
Acquiring Birthright increases the chances of Malice kills dropping Half Black Hearts to 35%.

Additionally, it grants each minion a special hat that grants different effects.

Astronaut
+10% tears.

Cat
+20% tears.
-1 luck.

Fedora
+10% damage.
+1 luck.

Flower
+4 luck.

Football
+10% damage.
-1 luck.
+25% tear size.

Ghastly
x2 damage.
-90% tears.

Goggles
+50% tears.
-25% damage.
-25% tear size.

Plumber
+1 luck.
-5% tear size.

Viking
+20% damage.
-10% tears.

Visor
+75% tear size.

Open up the hidden Red Door in the Home level as Fiend.

The following special synergies and interactions for Tainted Fiend have been documented.

* Note that not all possible synergies and interactions are listed here.

• Check out the character description on the mod's external Wiki.
• Download Fiend Folio from the Steam Workshop.