Warpfire Venom (5e Equipment)
From D&D Wiki
Price per dose: 900 gp
Crafted with an eldritch and cruel form of alchemy, warpfire venom is a deadly cocktail of poisons both magical and mundane, bound together and enhanced by harnessing the strange forces of powdered warpstone. Though there are many counterfeits, genuine warpfire venom can be identified by its sickly green coloration, and its almost imperceptible glow of sallow light. The recipe to craft warpfire venom is a well-kept secret shared by the Eshin Assassins and the mad alchemists of Skryre, both rumored to be composed solely of wererats. Attempting to craft warpfire venom without the recipe is foolish beyond belief, as failure is all but sure to kill any who attempt it. Still, certain individuals of particular talent may well glean the secret by invitation into one of the two orders - if, that is, they are willing to pay the price.
A creature subjected to this poison must make a DC 17 Constitution saving throw or take 5d6 poison damage and become poisoned for 1 minute. On a successful save, the creature takes half damage and is not poisoned. If the saving throw fails by 5 or more, the creature is also incapacitated while poisoned in this way, as agonizing eldritch green flames erupt from their bodies. Most creatures subjected to this effect tend to run around madly or writhe on the ground, screaming. The flames are magical, and cannot be dispelled by normal means; a creature suffering from this effect can repeat the Constitution saving throw at disadvantage at the end of each of their turns to end this effect.