Evasion. If Vipers are subjected to an effect that allows them to make a Dexterity saving throw to take only half damage, they instead takes no damage if they succeed on the saving throw, and only half damage if they fail. They can’t use this trait if they're incapacitated.

Sneak Attack (1/Turn). Vipers deal an extra 14 (4d6) damage when they hit a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of a Viper that isn’t incapacitated and if the Viper doesn't have disadvantage on the attack roll.

Multiattack. Vipers can make three attacks with their rapier or one attack with their hand crossbow.

Rapier. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 7 (1d6 + 4) piercing damage.

Hand Crossbow. Ranged Weapon Attack: +7 to hit, range 30/120 ft., one target. Hit: 7 (1d6 + 4) piercing damage.

Cunning Action. On each of their turns, Vipers can use a bonus action to take the Dash, Disengage, or Hide action.

Uncanny Dodge. Vipers half the damage that they take from an attack that hits them. They must be able to see the attacker.