Mortarion is the Leader of the Death Guard and Overlord of the Artificial Continent of Arcadia . He was formerly known as Lelouch vi Britannia, who became Zero to destroy the Empire. But at the end of the Black Rebellion, he was captured and had his memories rewritten to become a servant of the Empire. But this had the side-effect of turning him into the perfect killer when his memories were unlocked by C.C, causing him to abandon both the name of Lelouch and the mask of Zero, and began calling himself Mortarion, the Reaper.
Before he became Mortarion, Lelouch had the mindset of commander that was ruthless but fair. After he was brainwashed and pressed into the army, he kept this mindset, until a good friend sacrifised himself for him. He developed a Reaper Persona that came out in battle. This was so feared, even by his own troops, that his presence on the battlefield was dubbed as The Shadow of the Reaper. But when his memories from before his father´s Geass were unlocked, his mind went into turmoile. Having lived almost a decade of his new life, his new memories and old memories clashed. In the end, something snapped and he clung to the one thing he knew to be true, his Reaper Persona, the Shadow of the Reaper, Mortarion.
Mortarion's personality is nothing like Lelouch used to be. Where as Lelouch he was ruthless, but yet kind to those he cared about, Mortarion is now a ruthless killer that stops for nothing. He is cold, precise and doesn't hesitate to sacrifice civilians to achieve his goals. If it would lead him to victory, he would turn an entire city into a death trap,trapping his foes inside and then systematically bombarding it until they are destroyed, headless of any civilians inside. He also doesn't care about his family anymore. He once said that he would kill them without a second thought if they ever stood in his way, or if it would deliver him the victory.
Mortarion is very different from when he was known as Lelouch.
Mortarion is incredibly skilled in piloting his chosen Knightmare Frames. Where as Lelouch he always remained in the back, as Mortarion he always stays on the frontline, fighting with his men with ruthless efficiency. His skills are such that he is said to be on par with the Knights of the Rounds, a fact that even the Knight of Ten, Luciano Bradly admits after Lelouch beat him in a training mission.
Mortarion is far more capable in Close Combat and in the Physical aspect. He can easily outfight most soldiers due to intense training and Bionic Experiments. He can easily carry weapons a normal soldier would nead a tripod for on his own. He can even shatter rocks with a simple punch. While he is good in Martial Arts, he is no match for prodigies like Suzaku Kururugi and Kallen Kozuki in terms of skill and finesse. In the strength department he far outclashed them now. While they have the speed and flexibility to dodge his attacks, Mortarion only needs one direct hit to knock them out.
Mortarion is extremely skilled with the weapons he and his troops use, but even more with his preffered weapons, Silence and The Lantarn. Aside from these he prefers to use a combination of Close Combat Weapons and Sidearms like handguns, or, in his case, even Assault Rifles and Grenade Launchers. His skill with his scythe is said to eclipse even Bismarck Waldstein´s and Suzaku Kururgi´s skills with a sword.
Mortarion has a Geass,but not the same one. After the memory wipe, his Geass was sealed. He made a contract with V.V for a new one. This geass was the Power of Absolute Distortion. It has the ability to distort space to achieve different feats. One of these is to transport his weapons to his side. Another is the reason he gained the name, The Shadow of the Reaper. With concentration he can distort space to appear where ever he wants. He can also create Vacuums to transport objects or to tear objects and people to pieces. The last is the power of Refraction, to change the trajectory of projectiles with his distortion of space, to a certain degree.
Silence is the massive scythe that Mortarion carries around as his weapon of choice. A massive weapon, as long as Mortarion is tall and with a large, deadly blade, Silence is the epitome of the Death Guard's Powered Weapon Technology. It is powerful enough to cut through the armor of a Gloucester like it was made of wet paper, and even the armor of more advanced Knightmare Frames falls to the deadly blade. He can also overcharge the powerfield to fire a hazy wave of energy that slices through pretty much any mundane material.
The Lantern is a hand held, drum barreled Energy Weapon, as well as the only man portable Hadron Cannon in existence. It was custom made for Mortarion by Camelot under supervision of Llyod Asplund and only someone with his strength could even hope to fire it without any side-effects. Unlike the Knightmare Frame mounted Hadron Weapons, The Lantern can switch between a continous beam and sphere like blasts. While not as powerful as the Hadron Cannons installed on Knightmare Frames, it is still powerful enough to blow a hole through 3 Sutherlands in a row and the spheres are still strong enough to cripple or even destroy most Mass Produced Frames. By overcharging the gun, it can fire a Hadron Beam of the same caliber as the Gawain, but it needs to recharge for a while after firing.