Swinger
Swingers are enemies that consist of a separate head and a body, both connected with a long cord. Both parts can be separately damaged and once either is killed, the remaining part can split off.
This page is about Swingers added by Fiend Folio. More information about Swingers in general can be found in the vanilla page.
Flailer
Flailers are a variant of Swingers that feature a 
Fistuloid as a head instead of a 
Maw. The body will slowly slide towards Isaac, with the Fistuloid head drifting away from the pile and closer towards him. Once the neck has been extended a Flailer will perform an attack depending on their distance to Isaac:
- If Isaac is close, they will slam their head away from, then back onto Isaac, sending 4 projectiles in the ordinal directions with the second slam.
- If Isaac is far away, they will spin their head counterclockwise constantly firing projectiles outwards as they do. They will make 4 full rotations before stopping.
- However, if the head hits a wall during the spin, the attack will be interrupted and it will send out 4 projectiles in a spread in the opposite direction and spawn a
Leper Flesh at the point of impact.
- However, if the head hits a wall during the spin, the attack will be interrupted and it will send out 4 projectiles in a spread in the opposite direction and spawn a
If a Flailer's body is destroyed first, the head will transform into a regular Fistuloid. If the head is killed first, it will send out a Chubber projectile in the cardinal direction closest to Isaac, as a regular Fistuloid would on death, while the body transforms into a 
Globin in its goo form.
Rotspin
Rotspins are rotten variants of Swingers, found in Corpse. They can spawn with up to 4 heads, which will extend outwards from the body and orbit it. Multiple heads will be evenly spaced from each other, and each head will also constantly emit a trail of toxic gas clouds as it spins. Unlike their counterparts, their bodies will not follow Isaac and instead slide randomly around the room in the cardinal directions.
If the body is destroyed, the remaining heads will burst, creating a long-lasting toxic gas cloud and spawning 4 
Small Maggots each. If a head is destroyed, it will still create a cloud of gas and spawn maggots. Once all heads are destroyed, the body will reform into a 
Spoilie.
Trivia
- Flailer's attacks are based on those of Bertran, a modded character.
- Flailers were unused in the AB+ release of Fiend Folio.
