The Dark Sorceress is the main antagonist of Avalon: Web of Magic. Her first name is Miranda (Moranda in the upcoming/canceled animated series), though she is rarely called that. She was inspired by both Lady Kale and Morgana from Princess Gwenevere and the Jewel Riders.
The Dark Sorceress is a corrupted mage and was actually one of the chosen mages before the heroines Emily, Adriane, and Kara (her niece). She is a rogue magic user who uses magic for her own gain, solitary and spiteful. Miranda formerly ruled over the Shadowlands and the Otherworlds. She also formerly worked with the Spider Witch.
Miranda became the Dark Mage out of her and her sister Lucinda's Party. Driven by jealousy, and her twisting the meaning of the Prophecy of Avalon, she killed her bonded, Faylinn, and took her magic, twisting her own magic dark and eventually changing her into the Dark Sorceress.