Weresnake
Weresnakes, also known as Wereserpents, are any of a number of therianthrope strains that have the ability to partially or wholly assume the form of a snake.
In Dungeons & Dragons, wereserpents are native to the Forgotten Realms setting; they debuted in Dungeons & Dragons 3rd Edition in the Serpent Kingdoms splatbook, and were then updated to Dungeons & Dragons 4th Edition in the Forgotten Realms Campaign Guide.
Ravenloft is known to be home to at least two subspecies of weresnake created by fans in the Books of S; the Werecobra and the Wereanaconda.