Mortimer is the leader and founder of a Bolivian Tiberium cult operating in the vicinity of ancient temples, most importantly the Temple of the Tacitus, which houses the missing segment of the data matrix. He is bald headed and (possibly due to a unique Tiberium mutation) able to summon ion storms and influence his followers.
Nothing is known about Mortimer's life before the Ghost Stalker encountered him, his age is not known either, but it is possible he grew up near the end of the First Tiberium War, granting him experience with the effects of Tiberium at an early age. It is unknown when his Tiberium Cult was formed or if he is its creator, However he is able to recruit roughly a few dozen members, perhaps more cultists that are unseen. Whether through sheer charisma or brainwashing tactics, Mortimer clearly has powers to make his followers fiercly loyal, to the point of commiting suicide upon his death.
Perhaps the most interesting and unexplained power of Mortimer is his manipulation of Tiberium, creating localised Ion Storms and taming Tiberium lifeforms, like the rest of his followers he is immune to Tiberium Poisoining, Despite not technically being considered Mutants. It is unknown if others possess powers similar to Mortimer's, however his existence made him the most powerful Tiberium controlling human, being stronger than Tratos and possibly Kane himself
During the operation to reclaim the second part of the Tacitus, Mortimer was assassinated as a neccesary step by the Ghost Stalker, during the remainder of the operation Mortimer's cultists commited mass suicide in his name. This is believed to be the end of Mortimer's Cult and their influence.
- If Mortimer is killed, any surviving followers will flock to his place of death and commit suicide.