Mummies are undead creatures that are deliberately created. They are usually created to guard tombs and the treasure buried therein, or in an attempt to grant eternal life to the deceased. Mummies are known to inflict a "curse," which is a disease that prevents those under it from healing. They are also known to be highly flammable, given the fact that they are very dry.
Mummies have been drained of all moisture, and their inner organs removed, but are shaped largely like they were in life, with skin and hair still attached, though often dry and flaking away. Mummies are wrapped in the funeral gear they were buried in, and frequently smell of spices, rather than rot.
Mummies first appeared in the OD&D White Box set, where their disease is mentioned, as is their vulnerability to fire.