Antibirth adds several new objects and obstacles to help or hinder Isaac's progress.
Objects
Charge Machine
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 machine is also able to add an extra level of charge to active items, like the Battery.
If destroyed, it drops several pickups.
It has a small chance to instantly kill Isaac, regardless of health. What exactly triggers this is still unknown.
Obstacles
Buckets
Buckets appear in Downpour, and act like regular rocks. Buckets have a chance to spawn the following when destroyed:
- Striders
- Small Leeches
- A few coins
- Leech familiar
Corpse Polyps
Corpse Polyps are green polyps that appear in the Corpse, and act like regular rocks. Corse Polyps have a chance to spawn the following when destroyed:
- 3 Small Maggots
- An explosive green shot
- Rotten Baby
- Rotten Meat
- Cancer
- Tinytoma
Spiked Rocks
Spiked rocks behave like regular rocks, but damage Isaac upon contact. They cannot be flown over.
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.
Teleporters
Teleporters appear in the Mausoleum. Stepping on one teleport pad transports Isaac to a different, matching pad.
Other
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 which kill an enemy in the room, usually when it's 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.