Mortanius is one of the key characters in the Legacy of Kain series. He was voiced by Tony Jay in Blood Omen and Alastair Duncan in Defiance.
Mortanius the Necomancer was born as the Guardian of the Pillar of Death during a time when vampires and humans lived in peace. Human guardians would be born and converted to vampires after they reached a suitable age. However, all this would change as Mortanius and Moebius
came under the influence of the Elder God
and decided to revolt against the vampires. The humans rallied together and claimed the Pillars as their own. This started an eternal war between these two races. Centuries would come to pass as the humans slowly forgot about the Pillar's true heritage.
Thirty years before the events of Blood Omen
, Mortanius was possessed by a Hylden lord (Hash'ak'gik) and killed the balance guardian , Ariel. Ariel's death sent her lover, Nupraptor into madness and he unleashed a pschyic attack against everyone in the Circle of Nine, including the newly born Balance Guardian Kain
.This act set Kain's destiny in motion. At the start of Blood Omen, Mortanius realized his mistakes and in repentence, decided to create the vampire's prophesied Scion of Balance by murduring the Balance Guardian Kain and resurrecting him as a vampire. This Scion of Balance was destined to bring the Pillars back to vampire guardianship. But Mortanius's plan was foiled by his old friend, Moebius (who still worshipped the Elder God). Moebius
into starting a genocidal crusade against his own kind which wiped out every vampire in Nosgoth, except Kain.
Meanwhile, Mortanius was slowly losing control of his body to a dark entity (the Hylden lord). He met the wraith Raziel
inside Avernus as he revealed how he had used the Heart of Darkness to create Kain in a plan to give the Pillars back to the vampires. Realizing he didn't have long before the dark entity would take over completely, he vanished and reappeared at the Pillars. There he argued with his fellow pillar guardian, Anarcrothe about the fate of the pillars. Their argument turned into a fight as Mortanius completely lost control and was taken over by the Hylden. Even his physical body was transformed into a demonic figure. The Hylden easy defeated Anarcrothe as Kain was secretly watching behind the pillars. After Anarcrothe 's demise, Kain came out and confronted the dark entity before defeating him in combat. Using the Soul Reaver, he destroyed the hylden and with it, Mortanius.