Medusa is one of the ghosts haunting the Haunted Mansion from the Disney Parks franchise, the Haunted Mansion.
Medusa appears briefly in the form of a portrait found in the mansion's portrait corridor where she appears in the form of a portrait. In the portrait, Medusa initially appears as a beautiful young maiden in ancient Greece but when the lightning flashes she transforms into a hideous gorgon. The original intention for the effect which can only be found in Phantom Manor, Medusa's portrait was intended to slowly morph from the beautiful maiden, into the hideous gorgon, into a stone statue of her monstrous state.
In her backstory from classical mythology Medusa was the beautiful demigod daughter of the primordial sea-gods Phorcys and Ceto and who would become the high-priestess of the wisdom/war goddess Athena. Much to Athena's anger Medusa was so beautiful and witty that the men who would come to the temple to worship Athena would make quips about how they should really be worshiping Medusa. So one day while walking along the beach, Medusa became "courted" by Athena's arch-rival Poseidon, the Lord of the Sea who decided that he would have Medusa as his lover to spite Athena. After having found the two in her temple, Athena took the opportunity to punish the priestess Medusa by transforming her into a hideous gorgon. As a gorgon, Medusa had snakes for hair, fangs, scaly skin, and eyes so horrifying that any mortal who looked upon her would become so petrified that they would transform into stone. After the punishment, Medusa went to live in hiding on an island and Athena sent several warriors and hunters to try and slay Medusa for glory and fame but all she sent would be killed by the tortured Medusa. That is until a demigod named Perseus decided to hunt Medusa as he needed her head to turn the sea monster Cetus into stone. Athena aided Perseus by giving him a reflective shield which he then used to keep track of Medusa's location while not looking at her directly so that he could decapitate her with his sword. After her death, Athena mounted Medusa's severed head on her shield.
Apparently Medusa's soul never moved on to the next life and her soul came to rest in the Haunted Mansion as one of several prominent ghosts from creepy old crypts all over the world.
In the Disney Kingdoms Haunted Mansion series, Medusa is one of the ghosts working for Captain Gore who wishes to use dark magic to capture and enslave the other ghosts in the Haunted Mansion out of pure envy. Medusa's motives in this story are unclear.