Gertrude

Is a man-made demon constructed by Claude. He was assembled using choice parts of demons that Claude stole or found. Since his parts are not his own, he spends life on the run from various demons wanting their respective parts back. Gertrude is looking for the recipe for his own creation in order to prevent further cases like his own, to learn more about himself, and also so that demons will stop trying to track him down.

He becomes more powerful during full moons, but has tended to avoid taking advantage of this as it will make him more violent. During these times, his usually silver hair will turn black due to the "evil aura." It is hinted by Puppen that Gertrude has been known to make human friends every so often, but that they don't last. Sahara's friendship is the first that lasted this long, and the first case where's he stayed in one place.

Gertrude has the ability to use anything he can assert power over by writing "Frailty, thy name is.." with his own blood.