A Yuan-ti warlock can arrange for captured human characters to be transformed into yuan-ti purebloods so they can roam freely within the Yuan-ti. To undergo the change, creatures must bathe with snakes in the blood of sacrificial victims while under the influence of temple drugs. The transformation leaves each creature with 1d6 levels of exhaustion. The transformation can be undone only by a wish spell or divine intervention. Characters who survive it gain a random form of indefinite madness (see “Madness” in chapter 8 of the Dungeon Master’s Guide). A human that undergoes and survives the ritual retains its traits and gains the following yuan-ti racial traits.

Darkvision. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

Innate Spellcasting. You know the poison spray cantrip. You can cast animal friendship an unlimited number of times with this trait, but you can target only snakes with it. Starting at 3rd level, you can also cast suggestion with this trait. Once you cast it, you can’t do so again until you finish a long rest. Charisma is your spellcasting ability for these spells.

Magic Resistance. You have advantage on saving throws against spells and other magical effects.

Poison Immunity. You are immune to poison damage and the poisoned condition.