Mephistopheles is a large, black cat, with longish fur.  He is very much a "gentle giant", slow to anger and, until he does, generally friendly and good natured.

When something does spark his ire, though, he is a dangerous fighter.

He was born, as he will gladly tell anybody who asks, on a front porch, on a cool, clear evening in the early fall, just as the first star was winking to life.  His mother saw the star appear as he was born, and later told him it was important, and meant that luck would follow him all of his lives.

He can often be found sitting on the warm hood of a car, thinking, and claims that the warmth encourages his best ideas.