Mummies are the mummified remains of a creature that has long since died. They are reborn with only one goal in their mind, this goal being whatever they were trying to accomplish at the time of their death. They can do anything they want, but the need to complete that goal consumes all, and once that goal is completed, they return to their resting place.
Mummification is not practiced on The Makai, so they exist solely on Earth