The Fistuloid flies towards Isaac in an erratic waving motion. When it gets close to Isaac, it fires a blood shot at him and propels itself in the opposite direction. Upon death, it fires a maggot that flies off screen. The maggot is fired in the cardinal direction closest to Isaac, and will deal a full heart of damage if touched.
- Fistuloids were added in Booster Pack #4.
- Fistuloids appear to be small Fistulas with a Chubber's charger stuck inside.
- Matriarch, added in the Booster Pack after which this enemy was added, is designed in a way which resembles a larger version of a Fistuloid.
| Booster Packs
- Angry Fly
Spawns a fly familiar that orbits around a random enemy and deals 5 damage per tick to enemies it comes in contact with.
- Black Hole
Throws a black hole on the ground which sucks in and damages enemies.
Increases damage by a flat 0.1 and grants a soul heart. Enemies can randomly become briefly charmed or feared. Taking damage has a chance to spawn a rainbow poop.
- Broken Modem
Enemies, enemy shots, tears, and pickups will briefly freeze in place at random intervals.
- Mystery Gift
Upon use, spawns a random item from the current room's item pool, with a chance to spawn A Lump of Coal or The Poop instead.
Upon use, spawns a sprinkler that rotates and fires tears.
- Fast Bombs
Grants 7 bombs and allows bombs to be placed rapidly.
- Buddy in a Box
Grants a familiar with a random tear effect. The familiar is randomized at the start of each floor.
- Lil Delirium
Grants a familiar that transforms into another random familiar every 10 seconds.
- HairpinFully recharges Isaac's active item upon entering a boss fight.
- Wooden CrossGrants a Holy Mantle shield upon entering a new floor, which protects against one hit of damage.
- Butter!Using an active item will drop it onto a pedestal on the ground. Taking damage may result in dropping a passive item.
- Huge GrowthMakes Isaac large for the current room, increasing his range and damage.
- Ancient RecallSpawns 3 random cards.
- Era WalkFor the current room, enemies are slowed, Isaac's speed is increased, and his shot speed is decreased.
- Jumper Cables
Grants an active item charge every 15 enemies killed.
Upon use, makes a random item from a shop, devil deal, or black market free.
Upon use, for the next two seconds, any enemy shots that come near Isaac are held in place. After the charge is depleted, they are fired back as tears.
- Moving Box
If the box is empty, picks up all items and pickups in a room and stores them. If the box is not empty, places all stored items and pickups in the current room.
- Technology Zero
Connects Isaac's tears with electricity that can damage enemies.
Upon taking damage, grants a body part as an orbital, which blocks enemy shots and deals 7 damage per tick to enemies it comes in contact with. The orbitals will be destroyed if they take enough damage from enemies or enemy shots.
- Filigree FeatherAngels drop items instead of key pieces when defeated.
- 7 Seals
Grants a random Harbinger familiar that changes every 10 seconds.
- Mr. ME!
Summons a controllable ghost that can perform various tasks depending on what it targets.
- Angelic Prism
Grants a prism orbital with a large orbital radius. Tears that pass through the prism split into four multi-colored tears.
Replaces Isaac's tears with eyeballs that can bounce off of each other. The eyeballs are not limited by range, and will instead dissipate when they stop moving or when hitting an enemy or obstacle.
- Door StopThe last door Isaac went through stays open, allowing him to leave the room even if enemies are in it.
- Death's List
Grants a reward if all enemies in a room are killed in the order they are marked.
Tears are now fired in an arc. Upon hitting the floor, an obstacle, or an enemy, they burst into many smaller tears in all directions. Increases tear delay.
Isaac's tears decelerate as they travel. Upon stopping or hitting an obstacle, they burst into 8 tears in all directions. Tears can be fired into other tears to feed them, increasing their damage.
Tears are replaced with piercing white blasts of light.
Allows Isaac to hold two active items.
- Extension CordBeams of yellow electricity flow between Isaac and his familiars, damaging any enemies between them.
Grants one soul heart. Upon entering a boss room, grants a shield that blocks one hit, then disappears.
- Sacrificial Altar
Upon use, sacrifices up to 2 familiars and spawns an item from the Devil Room Pool for each familiar sacrificed.
- Lil Spewer
Spawns a random pill, and grants a small Spewer familiar that charges up and fires different types of creep.
Spawns 3 random trinkets. Taking damage has a small chance to swallow Isaac's currently held trinket, gaining its effect permanently.
- Mystery Egg
Spawns an egg familiar, which cracks and turns into a random friendly enemy when Isaac is hurt. The egg regenerates upon entering a different room.
- Flat Stone
Tears bounce off the floor. Tears that hit an enemy after bouncing deal splash damage to all nearby enemies for 25% of Isaac's tear damage.
Grants one bone heart and spawns three red heart pickups.
- Slipped Rib
Spawns a bone familiar that circles around Isaac and reflects enemy shots.
- Hallowed Ground
Spawns a white poop familiar, which turns into a white poop when Isaac is hurt.
- Pointy Rib
Spawns a bone familiar that can be aimed with the fire buttons and does contact damage.
- Book of the Dead
Upon use, spawns a friendly Bony or an orbital bone for each enemy killed in the current room.
- Dad's Ring
Creates a ring of light around Isaac that petrifies enemies in contact.
- Divorce Papers
Spawns a Mysterious Paper, increases tears, and grants a bone heart.
- Jaw Bone
Spawns a familiar that flies the room while firing, dealing a flat 7 damage to enemies that come in contact and retrieving pickups.
- Brittle Bones
Replaces all red hearts with 6 empty bone hearts. Upon losing a bone heart, Isaac fires bones in 8 directions and permanently gains a tears up.
- Broken Shovel
While held, causes multiple Mom's Foots to come down and stomp on Isaac. One of two parts necessary to create Mom's Shovel.
- Broken Shovel
One of two parts necessary to create Mom's Shovel.
- Mom's Shovel
Spawns a trapdoor that leads to the next floor upon activation. Unlocks The Forgotten when used on a mound of dirt that appears in The Dark Room.
- Rotten PennySpawns a blue fly every time a coin is picked up.
- Baby-BenderGrants Isaac's familiars homing shots.
- Finger BoneGrants a chance to gain a bone heart upon taking damage.