Dalton
What's my line - Part 1, Surprise
Although Dalton is a vampire who has a demon in place of his soul, he is fairly harmless (from what we have seen anyway).
Dalton has a love of books and reading. He was selected to translate the duLac Manuscript for Spike and Drusilla, but was unsuccessful without 'the key'.
Dalton was next seen aiding Spike in retrieving the boxes for Drusilla's present which was a demon named the Judge.
The Judge destroys people or creatures by burning the humanity out of them. Dalton was chosen for the burning due to his love of books, thus destroying this harmless vamp.