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| Defeat Delirium as ???King Baby|
King Baby is an unlockable passive item added in Afterbirth †.
- Grants a familiar that follows Isaac and always appears first in the familiar chain.
- While firing tears, King Baby stops moving and glows white.
- While King Baby is stationary, other familiars remain stationary as well. Shooting familiars will fire tears in the direction the player is firing.
- When Isaac stops firing tears, King Baby moves rapidly back towards Isaac.
- King Baby will move back towards Isaac during Isaac's hurt animation, even if a fire button is still being held.
- AbelA familiar that mirrors the player's movements and shoots in the opposite direction. will still reflect Isaac's movements, and not King Baby ones.
- Lil DeliriumGrants a familiar that transforms into another random familiar every 10 seconds. depends on which familiar form it takes.
- Familiars unaffected by King Baby include:
- ???'s Only FriendSummons a big attack fly that can be controlled with the shooting direction-keys.
- ???'s SoulSpawns a familiar that floats slowly around the room on a pattern similar to The Peeper and fires spectral and homing tears.
- 7 SealsGrants a random Harbinger familiar that changes every 10 seconds.
- Angelic PrismGrants a prism orbital with a large orbital radius. Tears that pass through the prism split into four multi-colored tears.
- Angry FlySpawns a fly familiar that orbits around a random enemy and deals 5 damage per tick to enemies it comes in contact with.
- BBFSpawns a familiar that flies around the room in a manner similar to the Boom Fly and explodes on contact with an enemy. Respawns after ten seconds.
- Big ChubbySpawns a familiar that slowly charges forward and damages enemies in its path.
- Bob's BrainSpawns a familiar that charges forward when shooting tears and explodes upon contact with an enemy, damaging and poisoning them. The familiar respawns after a few seconds.
- Bum FriendA portable beggar who follows Isaac, picks up coins for himself, and occasionally drops a pickup after collecting a coin. Does not spawn collectibles.
- BumboSpawns a beggar familiar which floats around the room and picks up any nearby coins, leveling up after collecting several coins. At level 2, Bumbo gains a body. At level 3, it begins to fire tears. At level 4, Bumbo chases enemies slowly, dealing contact damage.
- Cain's Other EyeSpawns a familiar that floats slowly around the room on a zig-zag pattern similar to The Peeper and shoots normal tears in the same direction as Isaac.
- Daddy LonglegsDaddy Long Legs' shadow follows Isaac and stomps on enemies.
- Dark BumSpawns a familiar that follows Isaac around and collects red hearts. For every one-and-a-half red hearts collected, Dark Bum will generate one soul heart, one hostile Spider or one friendly blue spider.
- Dead BirdSpawns a flying familiar for the current room that chases enemies whenever Isaac takes damage.
- Finger!Spawns a finger familiar that points at enemies, dealing constant damage.
- GB BugA glitch familiar that bounces around the room and applies a random status effect to any enemies it comes into contact with and has a chance to re-roll pickups that it passes over.
- GeminiSuture becomes attached to Isaac, and does touch damage to enemies within its attacking range.
- Guppy's Hair BallLoosely follows behind Isaac. Can be swung like a flail by rapidly spinning Isaac in a circle. Grows bigger by killing enemies.
- Jaw BoneSpawns a familiar that flies the room while firing, dealing double Isaac's tear damage to enemies that come in contact and retrieving pickups.
- Key BumSpawns a portable key master that follows Isaac and collects keys, giving random chests in return.
- LeechSpawns a friendly familiar leech on the ground that hunts down enemies and heals you for half a heart each time it eats one.
- Lil GurdyGives Isaac a Gurdy familiar that will charge around the room dealing contact damage to enemies. Lil Gurdy is charged by holding down a fire button and letting go. The longer the button is held, the faster Lil Gurdy will fling itself across the screen. Lil Gurdy can pass over objects and obstacles in the room.
- Lil HauntA familiar that damages enemies by chasing them as well as inducing the fear effect.
- Little ChubbyA familiar that charges forward and deals touch damage to any enemies in its path.
- Multidimensional BabySpawns a familiar that will follow Isaac's movements on a 2.5 second delay. Tears that pass through the baby will be doubled and increase in speed.
- Obsessed FanA purple fly familiar that follows Isaac's movements on a 3 second delay and deals contact damage to enemies.
- Orbital familiars
- Papa FlyA blue fly familiar follows Isaac's movements on a 3 second delay. Papa Fly will fire tears at nearby enemies.
- The PeeperSpawns a familiar that floats slowly around the room on a zig-zag pattern similar to Boom Flies damaging enemies it passes through.
- Pointy RibSpawns a bone familiar that can be aimed with the fire buttons and does contact damage.
- Samson's ChainsPull a chain and ball behind you that will damage enemies on contact and is able to break stones.
- ShadeSpawns a shadow familiar that follows Isaac's movements on a 1 second delay and deals contact damage to enemies.
- Sissy LonglegsWanders about the room, occasionally spawning blue spiders.
- Smart FlyAfter Isaac takes damage, this fly will deal continuous touch damage to whatever enemy caused the damage until it is dead. The fly will then systematically attack 1 enemy at a time until the room is cleared.
- Spider ModDisplays Isaac's tear damage and enemy health bars. Spawns a gray spider familiar that wanders around and inflicts a random status effect on any enemies it comes into contact with. Occasionally spawns a blue spider upon clearing a room.
- SuccubusSpawns a flying familiar that bounces around the room with a black aura, dealing rapid damage to any enemies inside it. While standing in the aura, Isaac gains a 1.5x tear damage multiplier.
- Super Bum
- Temporary familiars
- YO LISTEN!+1 luck. Spawns a fairy familiar that points out secret room entrances and tinted rocks.
- Isaac's HeartIsaac himself is now immune to all damage, and a heart familiar appears and follows Isaac. If the heart is hurt, Isaac is hurt.: Isaac can fire tears and leave King Baby and the heart behind, and run into a group of enemies without being damaged.
- BFFS!Increases the size and damage of familiars.: Increases King Baby's size. No other effect.
- DiplopiaDuplicates all pickups and item pedestals in the room.: Whichever King Baby was picked up first will be in front. Stationary effect applies to both of them.
- Duct TapeStops Isaac's familiars from moving.: King Baby will stay in place relative to Isaac until Isaac starts firing tears. Then King Baby will remain stationary until Isaac has stopped firing and will rapidly move back to him.