Chevill

Improved Assassinate. Chevill has advantage on attack rolls against any creature that hasn't taken a turn. Any hit Chevill scores against a surprised creature is a critical hit.

Evasion. If Chevill is subjected to an effect that allows him to make a Dexterity saving throw to take only half damage, Chevill instead takes no damage if he succeeds on the saving throw, and only half damage if he fails.

Improved Sneak Attack. Chevill deals an extra 21 (6d6) damage when he hits a target with a weapon attack and has advantage on the attack roll, or when his target is within 5 feet of an ally of his that isn't incapacitated and Chevill doesn't have disadvantage on the attack roll.

Multiattack. Chevill makes two shortsword or crossbow attacks or one crossbow attack and one shortsword attack.

Shortsword. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) piercing damage + 24 (7d6) poison damage.

Light Crossbow. Ranged Weapon Attack: +7 to hit, range 80/320 ft., one target. Hit: 7 (1d8 + 3) piercing damage + 24 (7d6) poison damage.

Opportunity Attack Multiattack. Chevill makes two shortsword attacks as his opportunity attack.