Dark Entity of Avernus

Once more at the Pillars, Kain noticed his escaped prey Anarcrothe embroiled in an argument with Mortanius. Anarcrothe accused the necromancer of having rigged Kain's death and rebirth so that he could be used to purge the Circle of Nine. Mortanius acknowledged this truth and, after a brief and one-sided struggle, easily killed Anarcrothe himself to restore the Pillar of States.

After witnessing this, Kain confronted his alleged ally to learn that Mortanius did indeed arrange for all of this in order to cleanse Nosgoth and atone for his crimes against it. Revealing himself as the Guardian of Death, Mortanius welcomed his own death at Kain's hands but refused to simply go without a fight. Summoning skeletal creatures from the underworld, he beckoned Kain into battle.

Though Mortanius accepted his end, just before Kain dealt the killing blow, a monstrous voice echoed out from the man's throat. Years of possession by his 'god' Hash'Ak'Gik had finally taken its toll on Mortanius and his flesh rapidly mutated into that of a demonic horned creature. This entity revealed that it lied to and seduced Mortanius into its service, taking his body as host to arrange for the corruption of the Pillars and their Guardians, though he did not reveal his motives to Kain.

Despite utilizing Mortanius' own death magic to raise hordes of the dead against Kain, the entity was eventually defeated. Taking a mysterious magical orb from Mortanius' fallen corpse, Kain restored the Pillar of Death.