This item belongs to the Conjoined set. Collecting three items from this set will transform Isaac into a three-faced version of himself.
Notes
Killing the heads thrown by Rag Man before they turn into a Rag Man's Ragling is not counted as a kill and will not spawn a baby.
The same familiar can spawn multiple times.
Despite being stationary, tear-shooting babies will still inherit Isaac's movement, angling their tears accordingly.
Enemies killed by Dark Esau count as yours and will spawn a baby.
During The Beast fight, familiars spawned by Quints stay on screen throughout the chase sequence.
When playing as Tainted Lazarus, Quints will not disappear on Flip but instead give you the ability to spawn more Quints if you Flip again. This is very effective in Greed mode and Boss rush because you flip automatically when completing a wave, giving you more Quints for every other wave.
Synergies
Baby-Bender: All shooting familiars spawned are affected, save for Little Steven and Seraphim.
BFFS!: Affects Quints familiars, doubling their damage.
Quints: Lets you spawn an additional 5 Quints familiars per copy.
Interactions
Sacrificial Altar: The item will be lost, and each spawned familiar counts as one sacrifice. If Quints is sacrificed first (or is the only item available to sacrifice) and at least two familiars are summoned, two Devil Room items will be spawned while only losing one item.
Ace Cards: Enemies that are turned into pickups don’t leave familiars behind.
Box of Friends: Existing Quints familiars will not be duplicated, nor more will be created. If Isaac has no other familiars, the generated Demon Baby will hover with the Quints instead of following Isaac.
E. Coli/Flush!: Enemies that are turned into poop don't leave familiars behind.
King Baby: Familiars do not follow King Baby, nor are the familiars aiming independently at enemies.
Conjoined set. Collecting three items from this set will transform Isaac into a three-faced version of himself.
Rag Man before they turn into a 
Rag Man's Ragling is not counted as a kill and will not spawn a baby.
Dark Esau count as yours and will spawn a baby.
The Beast fight, familiars spawned by Quints stay on screen throughout the chase sequence.
Tainted Lazarus, Quints will not disappear on 
Flip but instead give you the ability to spawn more Quints if you Flip again. This is very effective in Greed mode and Boss rush because you flip automatically when completing a wave, giving you more Quints for every other wave.
Baby-Bender: All shooting familiars spawned are affected, save for Little Steven and Seraphim.
BFFS!: Affects Quints familiars, doubling their damage.
Quints: Lets you spawn an additional 5 Quints familiars per copy.
Sacrificial Altar: The item will be lost, and each spawned familiar counts as one sacrifice. If Quints is sacrificed first (or is the only item available to sacrifice) and at least two familiars are summoned, two Devil Room items will be spawned while only losing one item.
Box of Friends: Existing Quints familiars will not be duplicated, nor more will be created. If Isaac has no other familiars, the generated Demon Baby will hover with the Quints instead of following Isaac.
E. Coli/
Flush!: Enemies that are turned into poop don't leave familiars behind.
King Baby: Familiars do not follow King Baby, nor are the familiars aiming independently at enemies.
The Binding of Isaac: Rebirth
