Demilich

A monster in Dungeons and Dragons.

While a Demilich sounds like something that is a lesser form of a Lich, it is actually much more powerful.

A Demilich has been undead so long that most of his essence has transferred to the Negative Energy Plane, transcending his physical form. He is immune to most normal attacks and is capable of killing a person in many ways, including sucking out his soul.

A legendary Finnish death metal band.

Demilich plays technical and progressive metal with very low grunts and tuning. The Usenet heavy metal FAQ also classifies the band under post-modern and ambient metal.

Demilich released their only album Nespithe in 1993, and split up right after that. The last line-up consisted of:
Antti Boman - guitar and vocals
Mikko Virnes - drums
Aki Hytönen - guitar
Ville Koistinen - bass

The album gave the band a cult reputation, and rumors about reforming pop up every now and then.