Sucker

Suckers fly slowly towards Isaac and, upon death, fire 4 shots in the cardinal directions.

Notes

Suckers are unaffected by Skatole.
Suckers and all of its variants will not deal contact damage while Isaac holds Skatole, but can still deal damage by other means (usually by a bullet fired after death).

Variants

Spit

Spits fly slowly towards Isaac and, upon death, fire an explosive Ipecac shot toward him.

Ink

Inks fly slowly towards Isaac and, upon death, fire four projectiles in the ordinal directions and spawn a puddle of Black Creep.

Soul Sucker

Soul Suckers float towards Isaac and, upon death, spawn a swirling red vortex, which then fires four Brimstone beams in the cardinal directions after a short delay.

Notes

The Brimstone beams fired from the Soul Suckers can damage other enemies, including other Soul Suckers.
The appearance of the vortex resembles the same vortex that appears when firing Brimstone with the effects of Anti-Gravity.
They can spawn in unique Devil Room layouts if Isaac is holding the Number Magnet.

Mama Fly

Mama Flies float away from Isaac and occasionally stop to plant down a Pustule. They spawn Small Maggots upon death.

Notes

After planting a Pustule, they will move directly away from Isaac, and will continue in that direction until either planting another Pustule or hitting a wall.

Bulb

Bulbs fly in erratic, right-angled motions. If Isaac has an active item with any amount of charges (this includes timed recharge items), they fly towards him and drain up to 2 charges upon contact, but do not deal damage. If Isaac does not have an active item, or if his item has no charges, they simply fly around randomly and are completely harmless.

Notes

If Bulbs aren't unlocked yet, each will be replaced with a Fly.
Bethany's soul charges and Tainted Bethany's blood charges cannot be drained by them.
Bulbs replaced Greed Gapers in any Treasure Room layouts that previously contained them.

Bloodfly

Bloodflies are exclusively encountered in Corpse after a Pustule bursts. They behave very similarly to Bulbs in movement, but unlike Bulbs, don't drain charges and deal contact damage. After dying, they shoot 4 shots in the cardinal directions.

Tainted Sucker

Tainted Suckers float towards Isaac and, upon death, shoot 6 projectiles in all directions that bounce off of walls and obstacles, splitting into 6 smaller projectiles each.

They are exclusive to the Ascent to Home.

Notes

Strangely enough, they are the only Sucker variant aside from Bulbs that do not deal contact damage.

Gallery

Concept art for the Soul Sucker.
Concept art for the Bulb.
A Bulb after draining an active item's charges.
An aggressive Bloodfly.

Trivia

Suckers seem to be based on mosquitoes, midge-like flies that suck the blood of other animals, as they seem to share a small proboscis and blood sac.
Bulbs seem to be based on fireflies, with the positioning of their bulb mirroring the bioluminescent organ of the firefly.
The Sucker is tied with the Boom Fly for being the monster with the most true variants ('true variants' being monsters with ID x.1, x.2, etc), both with 7.
Soul Suckers were added in Booster Pack #4, after the initial release of the DLC Afterbirth †.
The Ink and Mama Fly first appeared in the Antibirth mod.
- The Mama Fly's AI has been changed from the mod where it would fly aimlessly rather than flying away from Isaac after planting down a Pustule.
Bulbs have a couple odd behaviors when converted into a friendly enemy by the Beelzebub transformation:
- If the room has no hostile enemies, they will still move erratically in Isaac's general direction regardless if he has charges or not (they will not steal charges while friendly).
- If the room has hostile enemies, they will erratically fly toward enemies; they deal no contact damage to enemies either, so this is useless and only results in their deaths.
Tainted Suckers have the lowest health out of any tainted variant.
The sound that plays when a Bulb dies is the same as when an active item charge was filled in the original Flash-based Binding of Isaac.