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.
Immortal Hearts replace Eternal Hearts with a 50% chance and do not spawn in any other way, except for one room in the Corpse.
Rotten Hearts are infested red hearts that 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 Isaac can have half a rotten heart. By taking any full heart source of damage with half a regular red heart next to a rotten heart, the rotten heart will appear "halved". This includes sources of damage after Mom and The Sharp Plug.
- A half Rotten Heart looks nearly identical to a half Red Heart, but it also spawns two blue flies. Grabbing a regular red heart will "repair" it. Taking half a heart of damage will destroy the half-rotten heart; however, taking a full heart of damage will deduct a full red heart in addition to the rotten heart.
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||Interacts with any machine or beggar in the room. Donates 7 coins to donation machines, plays beggars 6 times, plays blood machines 4 times, plays other machines 5 times. Machines and beggars have an increased chance to pay out or explode, even paying out at only one play.|
|Rune of Kenaz||61||"Pestilence"||2x. Scat Man||Poisons all enemies in the room for 48 hits. Seems to do between 1.0 and 3.5 damage per hit, but never scales off of Isaac's damage stat.|
|Rune of Fehu||62||"Wealth"||3x. Turbo||Turns all pickups or items in the room into coins. Coins generated are equal to how much the item would be worth in a shop (Items give 15 cents, trinkets give 5 cents, black hearts give 6 cents, 1+1 bombs/keys give 10 cents). Does not work on chests, open or closed, unless the chest has a pedestal item. Does not work with pickups or items not on the ground (Shop items, Devil deals).|
|Rune of Othala||63||"Legacy"||9x. Seeing Double||Gives Isaac a random item that he already holds. Items interact like how they would if you had gotten them from a pedestal.|
- The Rune of Fehu is similar to the Hermit? card introduced in Repentance.
- Shot Speed Up and Shot Speed Down were part of the Community Remix mod.
- Immortal hearts are one of the major additions to Antibirth that were not ported into Repentance.