In my dark fantasy universe the dark elves are incredibly vain and proud believing themselves to be the panicle of all living creatures.
They see all other living entities as lesser, imperfect and unworthy of their respect, they seek to purify the world by replacing all living creatures with warped and twisted versions of their own race.
Masters of alteration magic they dominate the lower classes into forced servitude and slavery.
Warping and twisting their servants for whatever purpose they desire, pain, torment, lust, or simply to satisfy their sadistically twisted sense of amusement.