Assassinate. During its first turn, the half-dragon has advantage on attack rolls against any creature that hasn't taken a turn. Any hit the half-dragon scores against a surprised creature is a critical hit.

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

Sneak Attack (1/Turn). The half-dragon deals an extra 14 (4d6) damage when it hits 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 the half-dragon that isn't incapacitated and the half-dragon doesn't have disadvantage on the attack roll.

Multiattack. The half-dragon makes two shortsword attacks.

Shortsword. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit:6 (1d6 + 3) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.

Light Crossbow. Ranged Weapon Attack: +6 to hit, range 80/320 ft., one target. Hit:7 (1d8 + 3) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 24 (7d6) poison damage on a failed save, or half as much damage on a successful one.

Poison Breath (Recharge 5–6). The half-dragon exhales poisonous gas in a 15-foot cone. Each creature in that area must make a DC 11 Constitution saving throw, taking 21 (6d6) poison damage on a failed save, or half as much damage on a successful one.