The Death Guardians’ had influence over the spirits and bodies of the dead. There were two guardians. The first is the original Vampire Death Guardian, called to serve the Pillars at the time of the Binding. The second is Mortanius, who served as Death Guardian until his demise in Blood Omen. It is debatable whether Kain killed Mortanius, or if he simply succumbed to the aggressive possession of the Dark Entity (the Hylden Lord). Whatever, as Mortanius died, the Dark Entity mutated his body into a demonic-looking form, and continued the fight with Kain at the Pillars.
known guardians were:
1.) unnamed, original vampire Death Guardian
2.) Mortanius the Necromancer