What race/species is Narberal? One underling of Momonga, Narberal Gamma (aka "Nabe"), accompanies him when he starts adventuring in episode 5. I'm guessing he chose her since she looks human and hence can blend in without needing full-body armor or illusion magic, as Momonga does, and as someone like Albedo or Demiurge would. 

That's all well and good, but Narberal clearly isn't actually human - she expresses her disgust for humankind on multiple occasions, and it's pretty clear that this isn't self-loathing. What is she?
According to the Overlord Wiki, Narberal Gamma's race is:


   a doppleganger battle maid