Nefarian is the current leader of the Black Dragonflight. He took over from the Ancient Black Wyrm, Annihilan, during the Great Dragon War.
Nefarian is a scientist at heart - he has majorly upgraded his home, Blackrock Mountain, with modern technology, including a working holographic computer display inside his inner sanctum. His stated goal is the perfection of the draconian species, via selective breeding and gene-splicing.
He employed the alchemist Ludevic, presumably for collaboration on Nefarian's main project, and to create skaabs. He has also worked with Patchouli Knowledge in the past.
Before his disappearance, he was last seen working with the ancient red wyrm, Groularougarn, to aid in the investigation of strange weather conditions on the red dragon's home.