When you take the Attack action against a surprised creature, the attack roll has advantage, and on a hit, the attack roll becomes a critical hit.
When you take the Attack action against a surprised creature using a weapon coated in poison and hit, you can cause the target to make a Constitution saving throw against your Intelligence DC. On a failed save, the attack's damage is doubled, and if the creature is wounded, it drops to 0 hit points. On a successful save, the creature is paralyzed until the end of your next turn.