Kirkessen the Zealous

A powerful lich who reported directly to the Lich King himself, Kirkessen the Zealous was instrumental in the Scourge's success in countless battles. Ultimately, he suffered a grievous blow from Lord Maxwell Tyrosus during a failed assault on Light's Hope Chapel, and is no longer able to assume a corporeal form.

Kirkessen is mentioned in the Compendium of Fallen Heroes found in Acherus, and is considered a hero by the Undead Scourge.

Adapted from wowpedia