One of the twelve elite Guardians appointed to safeguard the Holy Grail, Tallum was a veteran of Templar campaigns, gaining renown in the order. His key achievement was the Battle of Corinth, where together with Guy of Bramley he stood against Saracen warriors, outnumbered greatly. They felled a hundred warriors and routed another two hundred with their achievements. Their prowess made them a natural choice for being the Guardians of the Grail. Under Tobias de Treece, Tallum descended down into Aeternis, beginning the long vigil. Tallum's strength and ferocity only increased with time, especially due to the influence of the grail. When Malik's research into the Byzantines led him to doubt Tobias' rule, Tallum eventually threw his weight behind the rebellious templar and swore fealty to him alongside Claude Lancet, Vincent the Innocent, and Ewatt of Cloyes. Together with the rest, he worked on various projects for Malik, while their leader slowly divided them and tightened his grip on their minds. As the cult became increasingly depraved, so did Tallum's research - culminating in the first attempt to modify a knight directly using grailstone. Claude Lancet was the subject and Tallum turned him into an undead monster under Malik's guidance. He didn't care for anyone but himself at this point. The second attempt, on himself, was more successful, turning him into a fearsome giant.
Yet it did not improve his mental condition. If anything, it fractured it even more. When Tobias led the purge of Malik's court, after the man in question fled Aeternis, Tallum betrayed his best friend, Sir Guy, by locking him out of Aeternis, making return impossible and dooming him to death of old age. Worse, Tallum then pleaded with Tobias for mercy. He was contrite, claiming fear and folly, betraying others. It was all to save himself. Tallum pinned his abominable acts on the young Vincent the Innocent. The youth was then tortured for weeks, paying for Tallum's crimes against Claude and Guy. And while Vincent was murdered, he walked away.
But he did not walk away undamaged. As Malik's influence waned, his guilt waxed. Amplified by the grailstone, it reduced Tallum to a guilt-ridden killing machine. Stalking the corridors of Aeternis, Tallum hunts down beasts and trains continuously. As his "penance" continues, his mental state continues to deteriorate. The fate of Guy weighs the most on his mind and Tallum would give anything for a chance at reconciliation. The alternative is death in battle, an honorable exit from a dishonorable life. As such, he is almost totally devoid of humanity and the most alien of the knights, inhuman and frightening in the intensity of his anger and his passion for destruction. 
- Tallum is first encountered after leaving the cloister for the deeper levels. He ambushes you at close distance and attacks after a short conversation. There is a brief window of opportunity for neutralizing him with the elephant gun (equip it like an item, then enter aiming mode), although there's no benefit to doing so. If he "kills" you, you'll get to meet Tobias and explore the library.
- The next encounter is at the chapel, where he prays for a chance to make amends to Guy. It's possible to talk him down and even convince him to become an ally (the alternative is fleeing his rage; MS-7 Sniper is woefully inadequate for this huge mutant's armor). There's only one chain of dialogue options that will pacify him:
- What do you mean spying. You're somewhat paranoid aren't you?
- I mean simply that I intend no offence. And I apologise for disturbing your meditation. And for any misunderstanding when we met earlier.
- Because I have seen Guy! He succeeded in his pursuit of Malik. But only for long enough to gain sufficient grailstone to survive. Then the dog escaped him. He sent me down here knowing full well that outside of the influence of Malik, the knights good and true would return to their straight mind. In all truth, those were his very words to me.
- He sent me because Malik intends to try for the grail any day now. He said to remind you of the battle of Corinth. The two against many.
- There is nothing to forgive. My task is to guard the weakest access to the grail.
- At this point, Tallum will be pacified and will then move to the fight room to guard the most direct route to the grail. Take note, however, that when asking him questions it's very easy to provoke him into attacking. Any statement that might be interpreted as evidence of ignorance (after all, Guy would have told you about the guardians, Lurka, etc.) will be taken as such and the giant will attack.
- Otherwise, Tallum will only appear during the ending sequence (taking the route through the cathedral) and even then, only if you release Claude Lancet from his casket in the crypt. Tallum will be attacked by the undead knight and the two will go over the edge, clearing the way to the exit.
- Vincent: "The thieves. It has come to that time already then. But you will hear me? At last. (BREAK) Listen well, for I swear to you my innocence. (BREAK) Malik was the one, so convincing, insidious. He said that The Lord was an illusion, that his Maal was the only truth. That only the worship of grailstone was right. That it lifted the Byzantines to greatness, out of this hell. (BREAK) In the stronghold he prepared for us, he had many tablets from those that dwelt here before, deciphered, translated. Slowly, he divided us, sowing seeds of mistrust. Forcing us to work on isolated projects for him, telling us that Tobias had sworn slow deaths for us all and was constantly trying to invade the area. (BREAK) All I did was use his grailstone on plants, to make food for the armies he promised us he'd raise above ground. (Almost crying) But when he deserted us and Tobias captured us, one of the others sold me for their own survival. I didn't know. I tell you I didn't know. One of the experiments was on Claude. To turn him into...Horror. It was horror when I saw what was left of him. I told them it wasn't me. But they would have none of it. They tortured me for weeks, but I wouldn't confess. Even if I hadn't been innocent, they would have had nothing from me. (BREAK) Eventually, they tired and before my freshly dead eyes, they broke open my head and fed my brains to a hungry Theo. Then they powdered my skull and bones and ground them into the rock of this place so that my spirit could never leave with my remains. (By now he is openly weeping) Since then I have awaited the one person who will believe me and give me their blessing and the name of my true tormentor. The one that cast his own crime upon my head. Perhaps God will then let me sleep at last. (BREAK) Well, you have heard the truth. Do you believe me innocent?"
- Guy, Forgive Me
- Geffrye: "He is a mad dog. I have argued many times with Tobias, my superior the folly of having allowed him to live. When the followers of Malik were questioned, he was contrite, claiming fear and folly. He betrayed the hideous acts of the others. Tobias forgave him, but I do not trust him. He is insane."
- Design document: "Tallum is a cousin of William Oakenshield and was once a close friend and confidant of the late Richard of Bramley. He secretly shared Richard's doubts about the sanctity of their task, but never publicly stated these views for fear of reprisals from the others-particularly his cousin William whom he then greatly admired and slightly feared,
Thus Tallum was aware beforehand of the planned attack orchestrated by Mallik in 1753 and, although he took no part in it, he did nothing to prevent it. More importantly (and to his eternal shame) he did not forewarn Richard of the coming attack, He thus blames himself for Richard's death and believes himself to be both a coward and a traitor. Sadly the Grailstone built on this negativity and destroyed him, leaving an empty shell ofa man, completely consumed by guilt and bitterness.
Tallum is now a killing machine. He seeks only death in battle-an honourable exit from a dishonourable life. Totally devoid of humanity he is the most alien of the knights, inhuman and frightening in the intensity of his anger and his passion for destruction. The only way a player can pass Tallum without violence is to mention Richard's name, or to imply that he/she is carrying out his dying wishes. Tallum might see this as a chance to right the wrong he thinks he has done, and may be of dramatic assistance, particularly against William Oakenshield, whom he now secretly hates and blames for all his problems."
- Tallum: "Since Mallik and Guy left the temple, things have been much as they were at that time. Edgar and Philip maintain their obsession with keeping the faction alive, while Tobias lives as always amongst his books, worshipped by the fool Geffrye and his twisted little dog Lurka. Meanwhile I have wandered the temple having little to do with them. I occupy most of my time keeping and training to the best of my ability the Theos and other beasts of the temple. I do this for Tobias. It is his punishment for my past foolishness in being a party to Mallik's dreams of power."