In Vonda McIntyre’s novel Dreamsnake a herpetologist/healer (also, rather creatively, named Snake) on a post-apocalyptic Earth relies on Mist, an albino cobra, Sand, a rattlesnake, and Grass, an alien creature that resembles a snake, to cure the patients she meets. By feeding them different chemical concoctions, their venom becomes a means of healing rather than death.
In real life, venomous snakes are some of the most feared creatures known. As many as 94,000 people per year die worldwide because of snakebite. Most are located in rural areas where they do not have access to modern medical facilities where antivenom is available. In Quentin Tarantino’s Kill Bill movie duology, his assassins are named after snakes: Cottonmouth, Copperhead, Diamondback, Black Mamba, and California Mountain Snake, the latter species entirely fictional. (I suppose he might have meant the California Mountain Kingsnake, a look-alike for the very poisonous Coral Snake, and gotten confused. )
In the market for a deadly fictional snake of your own? Here’s a list of randomly generated made-up species.