Innate Spellcasting (Abomination Form Only). Primlak's innate spellcasting ability is Charisma (spell save DC 15). He can cast any spell up to spell level 7.

Magic Resistance Primlak has advantage on saving throws against spells and other magical effects.

Transform.  Primlak can drop his Abomination form and instead form his ghost to his liking, but he cannota attack much and can not cast any spells. He can only become the sizes: Medium and small. If he chooses to be medium, his AC is lowered to 15, and if he chooses small it gets higher: 20 AC.

Multiattack (Abomination Form Only). The yuan-ti makes two ranged attacks or three melee attacks, but can use its bite and constrict attacks only once each.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 7 (1d6 + 4) piercing damage plus 10 (3d6) poison damage.

Constrict. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 11 (2d6 + 4) bludgeoning damage, and the target is grappled (escape DC 14). Until this grapple ends, the target is restrained, and the yuan-ti can’t constrict another target.

Poison dagger (Abomination Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 16 (2d12 + 4) slashing damage.

Longbow (Abomination Form Only). Ranged Weapon Attack: +7 to hit, range 150/600 ft., one target. Hit: 16 (2d12 + 4) piercing damage plus 10 (3d6) poison damage.

Block  (Abomination form only). If a creature he focuses one of his heads to attacks, he can try to block it with his tail, to do this, he needs to do a constitution saving trow with dc 10 if it is a success, he is not damaged at all of that attack, but if he fails, he takes as much damage as ususal. He can only block once per round.

Yuan-ti summoning. He can, as an action, summon one Yuan-ti malison.