Mercurius

Mercurius is the non-magical and beloved pet cat of Winston. He is exceptionally large, exceptionally pushy (for a cat), and exceptionally playful, especially for his relatively old age.

He seems to get along well with Winston's phoenix mount, though not so well with Nora, who finds him a bit overwhelming.

On the other hand, Sandoval and many of the Sherwin cousins adore Mercurius and find him fascinating, having grown up mostly around demons and otherwise magical creatures.