Medusa are an all female race that combine humanoid and snake into a magical and powerful creature. They were most likely a creation of yuan-ti biomancy as they are able to breed with humans and true yuan-ti.
Medusa change as they grow older and more powerful. Young medusa may appear almost human except for their snakes for hair. As they mature though the snake features grow more obvious. They develop reptillian eyes and scaled skin. In the final stage, elder medusa’s legs fuse into a long serpent body below the waist. Medusa can live for centuries.
The ability of a medusa to turn victims to stone who meet their gaze is always on. They can not turn it off.