Blood Frenzy. The yuan-ti mutant has advantage on melee attack rolls against any creature that doesn't have all its hit points.

Spawn snakes. Summoning attack: the yuan-ti mutation rolls 1d20+5 and spawns that many HP worth of constrictor snakes. If cannot spawn any, next turn 1 spawns. Recharge on 5-6 on a D6

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one creature. Hit: 8 (1d6 + 4) piercing damage plus (3d6) poison damage (DC 14 Con save or half damage.)

Constrict. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 12 (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.