Muffin's age was not revealed, but Sadie has owned Muffin for six years, during which she was the host for Bast. Carter Kane noted that Muffin never seemed to age or grow. Muffin was given to Sadie by her father, Dr. Julius Kane.
Muffin is first seen when being thrown inside the Faust's home when Sadie meets Carter at the door. She is taken with the Kane siblings away from London to Brooklyn House by Amos Kane. When Sadie tries to enter Brooklyn House, Muffin puts up a fight until Amos allows her to enter. The next day, when the serpopards attack, Sadie asks Muffin for help. Muffin seems to explode with Bast standing in her place afterwards. When Bast combats Sobek, she sacrifices herself to protect Muffin as well as the Kane siblings. After being saved from the side of the river, Khufu takes her back to Brooklyn House. Upon Bast's resurrection, Muffin becomes her host once again. Muffin is mentioned quite a few times later, but has not appeared after Bast's resurrection.
Muffin did not stay cat for very long before turning into Bast, but in that time she was a anxious, fierce cat with an attachment to Sadie. Later, we learn this is because she promised Ruby and Julius Kane to protect Sadie, because she was Blood of the Pharaohs
Muffin has a yellow and black leopard-like coat, golden eyes, and pointy ears. A silver pendant of Bast dangles from her collar.
- Sadie formally brought Muffin everywhere she went.
- Muffin was gifted to Sadie by Julius Kane, Sadie's father.
- In Carter's view, Muffin never changes appearance.