Viper Khopesh

This curved blade was carved from a large viper's fang. When you hit with an attack using this magic sword, the target takes an extra 1d6 poison damage. In addition, when you roll a 20 on an attack roll made with this weapon against a Large or smaller creature, that creature must make a DC 15 Constitution saving throw. On a failed save, a creature takes 2d6 poison damage and is poisoned until the start of your next turn. The poisoned creature is incapacitated. On a successful save, a creature takes half as much poison damage and isn't poisoned.

Finesse: When making an attack with a finesse weapon, you use your choice of your Strength or Dexterity modifier for the attack and damage rolls. You must use the same modifier for both rolls.

Light: A light weapon is small and easy to handle, making it ideal for use when fighting with two weapons.

Proficiency: martial, scimitar Source: The Griffon's Saddlebag: Book Two p. 181 (Third Party)