Black Grail Knight
Grail Knights are considered the ultimate human warrior, if they fall they are given grand funerals and their souls belong to the Lady of the Lake. This process meant that normally, Grail Knights were one of the few beings who could not be brought into undeath, but some, particularly those whose corpses lay in Mousilion were vulnerable.
Taking up their fortress in Mousilion, the Knights of the Black Grail would become legendary. So deadly were the warriors, that many didn't even know they were knights, instead thinking that the "Black Grail" was an artifact of immense power and destruction. Many tried to defeat the undead order and all failed .
The Black Grail Knights were eventually destroyed by an army comprised of living Grail Knights and the mercenary forces of the Grudgebringers. With the Black Grail destroyed, they would finally find peace.