Medusas are monstrous beings with bodies that are covered in scales. Rather than hair, they have a writhing mass of serpents growing from their scalp. The eyes of a Medusa are feared. To look a Medusa in the eyes is to invite death, a females gaze will instantly transformed into lifeless stone, while a males will daze and weaken you.
Medusas are known and feared for there gaze attacks, it is possible to fight one blind but it is unwise. Medusa's are accomplished archers and shoot arrows poisoned with their own saliva. Medusa's prefer to live alone in small groups, but the desire wealth and most importantly power and influence. a group of Medusa's might rule over a terrified populace, or a single Medusa might be the head of an assassins guild.
Male's don't have the snake hair of their female counter parts but there blood is more poisonous. The petrifying effect of a female Medusa can be reversed by applying a few drops of the creatures blood to the victims lips and succeeding on a D20 heal check. the Medusa must have been killed within the past 24 hours for this to work.
References
2008 D&D 4th edition core product,Monster Manuel, pg. 186-187