A member of the M mummy monster class, is simply an artificially preserved version of another monster and superficially similar to zombies. However, Mummies tend to be stronger than their corresponding zombies.
Although mummies have been preserved, their flesh is nonetheless pre-aged and thus unsuitable for sacrificing, except for same-race sacrifices. They are also tainted, so consumption is only safe if it is tinned first. You can eat corpses from mummies without tinning them, if you manage to cure yourself using a unicorn horn, the cure sickness spell or prayer before you die of food poisoning, but this is a risky strategy, and any intrinsics you might gain from eating raw mummy could probably be obtained more easily and safely from another source.
All mummies are cold resistant.
If a player gets killed by a mummy, the bones file of that person will contain a mummy instead of a ghost. The character's items will then appear in the mummy's inventory rather than in a loot pile, so mummies in bones levels must usually be killed to get the late player's things.
Types of mummy
If you are human, eating a human mummy is considered cannibalism.
Giant mummies leave rotten giant corpses. These may be tinned and then eaten for the strength gain. Given their size, trying to eat the un-tinned corpse whole, expecting to have time to cure yourself afterward, is a bad idea.
A mummy is a corpse that has been preserved in some way, whether because of deliberate preparation (mummification) or because of environmental factors (such as low temperature or lack of moisture or oxygen) that prevented or slowed decomposition. The assumption that mummification rituals were intended to keep the body intact for eternity probably inspired the fictional concept of the undead mummy that can be reanimated because of the charms placed on it.
Mummies as a type of undead creature are sometimes only distinguishable from mindless zombies or fully sentient liches by being wrapped in cloth bandages. This image comes mainly from the mummies made by the ancient Egyptians, which were usually wrapped in linen. Not all cultures that practiced mummification used wrappings, however, and the term "mummy" is also applied to bodies that were preserved unintentionally, without preparations such as wrappings.
Mummies in NetHack are similar to Egyptian mummies in that they are wrapped, but they are probably not embalmed using strict Egyptian practices. NetHack mummies have brains that can be eaten by mind flayers; the Egyptian practice was to remove the brain before burial.
But for an account of the manner in which the body was
bandaged, and a list of the unguents and other materials
employed in the process, and the words of power which were
spoken as each bandage was laid in its place, we must have
recourse to a very interesting papyrus which has been edited
and translated by M. Maspero under the title of Le Rituel de
Everything that could be done to preserve the body was now
done, and every member of it was, by means of the words of
power which changed perishable substances into imperishable,
protected to all eternity; when the final covering of purple
or white linen had been fastened upon it, the body was ready
for the tomb.
Drow mummies are wrapped in spiderwebs (droven cloaks) rather than normal mummy wrappings.
Half-dragon zombies retain their half-dragon breath weapons.