So this has been bothering me, ever since I saw the Night Mothers body in Skyrim...

...In Oblivion, you go to the Night Mothers tomb, under a statue. She is a skeleton on an altar, surrounded by the skeletons of babies, supposedly the first sacrifices to Sithis. Her ghost even appears in this tomb, leading me to believe it IS her tomb...

In Skyrim, she has her skin. She just...magically grew her skin back, as a mummy.

What gives with this?

Perhaps Cicero travelled by way of Windhelm, and got some pointers from a certain serial killer about 'reskinning' ?

Alternatively, the Night Mother was on vacation during the Oblivion Crisis. That skeleton was actually her sister - the Night Aunt, if you will.

Who knows. The developers probably forgot the little detail.

Or they just thought a mummy would make for a better prop piece. It's such a small thing but it still makes me grind my teeth a little due to my ocd concerning inconsistencies.

They decided to use an existing model for Oblivion because they weren't anticipating doing a radical design change for Skyrim. She didn't have that fancy coffin in Oblivion, either.

Perhaps she can manifest herself in her tomb, due to its innate "unholiness".

The bit about maintaining her body as a conduit is new, too -- Bellamont attempts to kill a ghost in Oblivion, while by Skyrim's lore, he should have attacked her corpse.

A skeleton has nothing to maintain, remember. Just keeping the bones intact an all together, which is hardly enough devotion to establish Cicero's pseudo-Oedipus complex.