Fan Casting Adaptational Mundanity in Sort by Tropes

The great thing about a Fantasy Kitchen Sink setting is that you can introduce crazy new powers and foes at the drop of a hat. This, however, can make adaptions tricky, especially to exposition-unfriendly formats like movies. What happens then is that the character stays, but their fantastical elements are either toned down or removed. For example, a vampire would be downgraded to a serial killer who has a thing for drinking blood.