Agatha Harkness

Agatha Harkness is a fictional character, a powerful witch in the Marvel Comics universe. Supposedly, she was one of the original witches from the Salem Witch Trials in Salem, Massachusetts. She somehow survived and later became a significant figure in Marvel continuity, protecting Franklin Richards as his nanny and notably mentoring Wanda Maximoff (the Scarlet Witch) in real magic. She was eventually killed by Wanda, who went insane. She also had a familiar named Ebony, a weird cat-like creature that could sense the presence of mystical beings.