Mausoleum is a new environment added in Antibirth. It contains many necrotic-themed and psychic-themed enemies, as well as teleporters that can connect different parts of the same room or two different rooms. The Mausoleum is almost always segmented into two main areas. The primary area, where Isaac enters, contains a standard set of rooms along with a special teleporter room. The teleporter room requires Isaac to expend resources or maneuver through obstacles to reach a teleporter, which transports Isaac to the secondary area. The secondary area contains a few rewards, along with additional random special rooms.
Treasure rooms in the Mausoleum always have two items to choose from.
After "A Secret Exit" is unlocked, a locked door to the Mausoleum will appear upon completing The Depths, Necropolis, or Mines. The locked door requires two soul hearts, immortal, or black hearts to enter. The door will always take soul hearts before it takes black hearts, and black hearts before it takes immortal. If playing as Bethany, the door will instead take 4 charges from her counter, and if playing as The Lost, it is free to enter.
||Flies towards Isaac. Upon death, farts and sends out 6 blood shots in all directions.|
||Runs away from Isaac, occasionally spawning a Willo. Spawns a Willo upon death.|
||Appears out of a random bucket, then picks up and throws obstacles at Isaac. If the room has no usable obstacles, it will leave the room. If there are any Tinted Rocks in the room, it will wait until they are the last remaining obstacle, then attempt to flee with one of them.|
||Stationary enemy that protects any nearby enemies from damage.|
||Moves erratically around the room and charges toward Isaac when in line of sight. Can only be damaged from behind. Tears that hit its front are reflected and can damage Isaac.|
||Slowly walks towards Isaac. Occasionally fires a large bone which creates rock waves near its point of impact.|
||Bounces around the room diagonally. Occasionally pauses and creates a small fire underneath itself.|
||Rapidly moves around the room erratically and charges at Isaac if he comes within its line of sight.|
||Rapidly moves around the room erratically and charges at Isaac if he comes within its line of sight. The Bony on its back shoots at Isaac.|
||Chases Isaac, dealing a full heart of contact damage. Upon taking enough damage, it collapses into two piles of goo, which can be killed. Both piles can regenerate after a short period of time if not killed quickly.|
||Moves erratically around the room and can only be damaged from behind. Splits into an Empty Knight and a Pon upon death.|
||Moves erratically around the room and charges toward Isaac when in line of sight. Cannot be damaged, but will die if the corresponding Pon is killed.|
||Hops around the room, leaving pools of damaging red creep.|
||Summons ghost enemies such as Wizoobs, Lil' Haunts, and Candlers.|
||Moves around the room and charges at Isaac if he gets within its line of sight. If Isaac gets close, it lashes out with a short-ranged whip, which can damage Isaac and deflect projectiles.|
||Moves around the room and charges at Isaac if he gets within its line of sight. Constantly lashes out with its whip.|
||Moves around the room and charges at Isaac if he gets within its line of sight. If Isaac lines up with it horizontally or vertically, it lashes out with a long-range whip which can damage Isaac.|
||Summons skeleton enemies such as Bonies and Big Bonies.|
||Invulnerable enemies. Moves in a fixed pattern or rotates in a spot. If Isaac enters its light, it will lock all doors, summon enemies, and vanish.|
||Moves erratically. If Isaac gets near, it becomes stationary and starts breathing a stream of purple fire at Isaac.|
||Walks slowly around the room. If Isaac gets too close, it will scream, paralyzing Isaac. It will gain a slowing aura and start charging towards him.|
||Bounces around the room with a purple aura. If Isaac touches an aura, he will briefly become afraid, unable to fire tears. Dies when the room is cleared.|
||Walks horizontally or vertically, attempting to line up with Isaac. Frequently fires lines of four tears forwards.|
||Slowly floats towards Isaac and fires purple lasers. Occasionally teleports and reappears elsewhere. Has a chance to swap positions with Isaac.|
||Charges and fires a curving Brimstone laser when Isaac gets in its line of sight.|
||Periodically fires a rock wave forwards. Does not stop, even if the room is cleared.|
- Lil' Haunt
- Fat Sack
- Gaper (rare)
- Stone Grimace
- Psychic Maw
- Selfless Knight
- Floating Knight
|The Heretic||The Visage||The Siren||The Pile|
- Somewhere in the primary area of the floor, there will be a room containing many fireplaces. In the secondary area of the floor, there will be a room containing active and inactive teleporters in the same formation as the fireplaces. To acquire Knife Piece 3, put out the fires in the fireplace room that correspond with the inactive teleporters.
- When the heart boss fight inside the flesh room is defeated, all pickups and trinkets on the current Mausoleum floor will disappear.
- The track that plays in the Mausoleum is titled Machine In The Walls.
|Chapter 1||Chapter 2||Chapter 3||Chapter 4|