A undead corpse wrapped in bandages
The act of mummfication is an ancient form of burial used to preserve the corpses of highly ranked members of socieity sutch as kings, generals, priests etc. The corpse has serveral organs removed and is covered in chemicals that will make the corpse very durable from the test of time before being enwrapped by jewels and bandages. The final act was to put the mummy inside a luxurious cascet. Mummification was mostly common in Egypt and South America (Though there has been a few times where mummies where made in the Roman empire).
In many forms of media, mummies tends to be considered either completely unintimidating, lazy, slow and nearly immoble pushovers that are rendered useless once the bandages are off (this stereotype occours mostly in western cartoons sutch as Scooby Doo) or they are considered powerfull magicians and powerhouses that can even match vampires and demons in terms of destructive power. They seem to specialise mostly in spells that replicates the plauges of Egypt aswell as necromancery (the magic that summons zombies, skeletons, ghosts etc). However, the tend to sleep most of the time and not do mutch (as long as their tomb or treasures is left undisturbed)