I only know about protein-based snake venoms. As long as the snakes don’t pull the usual “biology is all about exceptions” card, we’re all good.
Search hard enough, and you’ll probably find one that is like a fat-soluble vitamin sort of venom. Maybe there also exists a snake that uses arsenic or plutonium as a venom. I mean, biology seems to go with the “why not” option more often than you would imagine.
