Antibirth adds a few new types of pickups.
Immortal Hearts are white hearts which append to the end of the health bar like soul hearts.
Immortal Hearts always take two hits to be fully depleted, and will regenerate from half to full upon clearing a room.
Rotten Hearts are infested red hearts which fill up a full heart container. If a Rotten Heart is picked up at full health, it will replace the rightmost red heart.
For each Rotten Heart possessed upon clearing a room, two blue flies will spawn. You cannot have half a Rotten Heart; they are always depleted in one hit.
Depleting a Rotten Heart will not count against Devil Deal Chance when it's the rightmost red heart.
Rotten Hearts are unlocked by entering the Corpse for the first time.
- Although a Rotten Heart is depleted in one hit, under certain circumstances you can have half a rotten heart. After you start taking a full heart damage from enemies, if you get damaged with a Rotten Heart next to half a red heart, the rotten heart will be damaged to half, instead of being destroyed fully.
- A half Rotten Heart looks identically to a half Red Heart, but it also spawns two blue flies. Grabbing half of a regular red heart will "repair" it. Taking half-a-heart damage will deduct half a heart of Isaac's health, however, taking full-heart damage will deduct 1.5 red hearts.
Three new pill effects were introduced in Antibirth.
|Shot Speed Down|
Decreases shot speed.
|Shot Speed Up|
Increases shot speed.
- It is possible for an Experimental Pill to decrease health while Isaac has one heart container, killing him.
|Rune||ID||Icon||Message||Unlocked by completing||Effect|
|Rune of Gebo||60||"Charity"||4x. Bloody Mary||Donates to a machine or beggar|
|Rune of Kenaz||61||"Pestilence"||2x. Scat Man||Poisons all enemies in the room|
|Rune of Fehu||62||"Wealth"||3x. Turbo||Turns all the pickups in the room into coins|
|Rune of Othala||63||"Legacy"||9x. Seeing Double||Rewards a random item that Isaac already holds|
|Rune of Ingwaz||64||"Treasure"|
|Rune of Sowilo||65||"Renewal"|