Objects

Antibirth adds several new objects and obstacles to help or hinder Isaac's progress.

Electrifier


Walking up to the machine and bumping into it will cost one penny. In exchange, the machine has a chance to recharge 1 to 3 charges of Isaac's currently held active item. It also has a chance to do nothing or harmlessly shock Isaac. The harmless shock has the same effects as Voodoo Pin, and will ignore Holy Mantle.

The machine is also able to add an extra two levels of charge to active items, similar to the Battery, with one extra level.

The machine will not charge Alabaster Box, instead always harmlessly shocking Isaac.

If destroyed, it drops several pickups.

Buckets


Buckets appear in Downpour, and act like regular pots. They also serve as hiding-spaces for Polties, which will occasionally come out of buckets a short time after entering a room.

Buckets have a chance to spawn the following when destroyed:
 * Striders
 * Small Leeches
 * A few coins
 * Swallowed Penny
 * Leech

Corpse Polyps


Corpse Polyps are green polyps that appear in the Corpse, and act like regular rocks. Corpse Polyps have a chance to spawn the following when destroyed:
 * 3 Small Maggots
 * A green Ipecac shot
 * Rotten Hearts
 * Rotten Baby
 * Rotten Meat
 * Cancer
 * Tinytoma

Spiked Rocks


Spiked rocks behave like regular rocks, but damage Isaac upon contact.

Red TNT


Red TNT barrels explode when destroyed. Unlike regular TNT barrels, red TNT only needs to be shot once to be detonated.

They also detonate if Isaac or an enemy walks into it.

Tall Blocks


Tall blocks are indestructible and impede movement, even if Isaac has flight.

If Isaac is under Mega Mush's effect, he can crush tall and regular metal blocks.

Tall blocks can be jumped over using How To Jump.

Teleporters


Teleporters appear in the Mausoleum. Stepping on one teleport pad transports Isaac to a different, matching pad.

Red Bombs


Red Bombs are special bombs found in the Mines. They can be picked up and thrown and will detonate after a short time even if still held. They cannot be carried between rooms.

Buttons
Antibirth adds many new functions to buttons. In some rooms, buttons can destroy certain rocks, create bridges across gaps, or spawn enemies.

A few rooms have red buttons that, when pressed, kill all vulnerable enemies in the room, usually when the enemies are unreachable by Isaac's tears.

Minecarts
Minecarts ride along rails in the Mines, carrying enemies, Grimaces and sometimes even fires along a fixed path. Minecarts are destroyed when the enemies inside are destroyed. If the Minecart was carrying a fireplace, the minecart will not be destroyed when the fire is put out.

Using The Poop, A Card Against Humanity, or finding a Brown Champion and covering a rail with poop can get carts to slip off and drive away from the room through the walls. Enemies automatically die once outside the screen.

Trivia

 * The Electrifier and Red TNT are the only obstacles that do not appear in Repentance. Electrifiers were replaced with Battery Bums, while Red TNT is not present in any form.