Serpent's Kiss

Serpent's Kiss is an unlockable passive item added in The Binding of Isaac: Afterbirth.

Effects[]

Grants a chance to fire poison tears, each tick dealing damage equal to Isaac's.
- Poison from the shots will tick 2 times.
Inflicts poison on enemies who make contact with Isaac.
- Contact poison will tick 6 times.
Enemies who are killed after they have been inflicted with this type of poison have a 20% chance to drop black hearts.
- Only applies to enemies after being inflicted with contact poison.
- Enemies still can drop black hearts if the poison has worn off

Not affected by luck.
The contact poison effect of this item is identical to The Virus.
Enemies and bosses with multiple segments, such as Chub and Larry Jr., have a chance to drop multiple Black Hearts.
The enemy does not need to be killed by the poison or still be poisoned when killed for the Black Hearts to drop.
Although Stonies and Shopkeepers can't be visibly poisoned, they still can drop Black Hearts if destroyed after being touched.
If a boss would have been poisoned, but negates it with status immunity, they can still drop a black heart.

Dr. Fetus / Epic Fetus: Bombs and missiles may become poisonous, and enemies hit by them may drop black hearts.
Invulnerability: Contact while invincible poisons enemies Enabling black heart drops
Mom's Knife: Enemies poisoned by the knife may drop black hearts.
Mars: Dashing into enemies will often both kill enemies, and cause them to drop black hearts.
Tainted Forgotten: Especially strong as you are likely to apply contact poison when attacking enemies, giving you black hearts frequently.

Godhead: The Godhead aura cannot inflict poison but the tears themselves may poison enemies on contact.
The following interactions are trivial in Repentance:
- Athame / Maw of the Void: The black rings may poison enemies but do not generate black hearts.
- Brimstone: The blood barrage may poison enemies but does not generate black hearts.
- Tech.5 / Tech X / Technology / Technology 2: The lasers may poison enemies but do not generate black hearts.
- Trisagion: May poison enemies but does not generate black hearts.

Serpent's Kiss is most likely referencing Viper (Madame Hydra) from Marvel Comics, who has green lipstick and has transmitted poison through hollow fangs or poisoned lipstick before.