As an action, you can make a melee weapon attack with a natural weapon in an attempt to inject venom. You must have a form of venom inherent to your body to use this maneuver. On a hit, the creature must make a Fortitude saving throw against poison (Difficulty equal to 8 + your Constitution + your proficiency bonus).
On a failed save, it takes poison damage equal to the stamina die and is poisoned for the duration.
On a successful save, it takes half as much damage.
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 by two dice for each additional stamina die expended.