"The Three Dees"

"What we mainly deal with are the Three Dees."

Giles furrowed his brows.

"What are they?"

"Well, there are Devils, which are the worst and most dangerous. That's fallen angels. Unbodied intelligences with a malevolent will; they hate everything but especially humans, seemingly, and have the cunning and malice to go at it hard. Then there's Daemons, which are what you might call spiritual animals, as it were. They arise out of nature and are attached to places and things. Mankind was supposed to be in charge of regulating them in the first place, but lost that ability a while ago."

The little man gave Giles a significant look.

"They're wild and kind of stupid, and every now and then one will break out like a fox in the henhouse and have to be whacked back into place. Then there's Dybbuks, which are the weakest but most common. That's dead people, or bits of them, that hang around after they should've passed on. You get your hauntings and obsessions and so on. Getting rid of Devils is rare and terrifying, like hunting tigers; dealing with Dybbuks is like cockroaches, rather personal and disgusting."

--from Under the Mountain, by T. M. Junge.