As a bonus action when you hit a creature with a melee attack made with a natural weapon, you can inject venom into its bloodstream. You must have a form of venom inherent to your body to use this maneuver. The target must make a Fortitude saving throw against poison (DC equal to 8 + your Constitution + your proficiency bonus).
On a failed save, the target takes poison damage equal to the stamina die and is poisoned for the duration. At the end of each of its turns, a poisoned creature can repeat the saving throw, ending the effect on itself on a success.
You can increase the damage for each additional stamina die expended.