There is, roughly, one and a half gallons of blood in a person's body, which is the perfect amount for an offering to a Daedric shrine. You'd better fetch your straw.

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:
There is, roughly, one and a half gallons of blood in a person's body, which is the perfect amount for an offering to a Daedric shrine. You'd better fetch your straw.