Medusa

Medusa is one of the Phantom Zone escapees who assists The Joker.

She is portrayed by Lauren White.

History
As a mythical Gorgon, Medusa has the power to instantly turn any creature that looks directly at her to solid stone. Some people might think of this as a curse, but she loves it, even if the effect does only last a few hours.

Unfortunately for her mischievous hobby, her legend has become so well-known that almost nobody falls into Medusa’s trap these days. She’s tried all kinds of tricks, like hiding behind bushes and suddenly jumping out, pretending to be inside a TV set, and going undercover in the reptile house at the zoo... but the hissing of her hair always gives her away!

The Lego Batman Movie
Medusa is a Master Builder, who was formerly a part of Metalbeard's crew. At some point, she became imprisoned in the Phantom Zone for her villainy and was a member of The Ubers.

When The Joker arrives, she and the others are at first going to eat him, until he offered to get them out. Medusa accepts his offer and is broken out. She assists him in his plan to take over Gotham City. In the end battle, she is egged by Egghead.