The hearts of the Dremora of Oblivion can be harvested as a powerful alchemical ingredient. While not as easily harvested, their bank accounts are also quite valuable when plundered.

Joke and fake loading screens and screenshots from The Elder Scrolls IV: Oblivion, run by @ChrisOfTheDead.
General links and the actual Oblivion mod made from these jokes in my Carrd page:
The hearts of the Dremora of Oblivion can be harvested as a powerful alchemical ingredient. While not as easily harvested, their bank accounts are also quite valuable when plundered.