|Taken Name||Walden D'Essai|
|Magic||Unknown before knowing his True Name|
Argeddion (also known as Walden D'Essai) is a Mage that had discovered his True Name. He believed in peace and attempted to use his powers to make everyone in the world magical - his vision of a peaceful world, which he thought would bring the human race into a new plane of existence. He was an immensely powerful sorcerer, with the same power level as Darquesse.
As Walden D'Essai
Argeddion, then known as Walden D'Essai, was a Mage searching for a way to make the world peaceful. During his studies, he discovered his True Name. During this time, he was dating Greta Dapple.
Because he discovered his True Name, Tyren Lament, Vernon Plight, Lenka Bazaar and Kalvin Accord retrieved him and placed him under an enforced coma. The group then traveled to the Himalayan Mountains to keep Argeddion out of harm's way.
In the Alps
Whilst in a coma, Argeddion transferred a portion his magic to mortals across the world, believing if everyone had magic the world would be perfect. He also manipulated Tryen and the group during his time in a coma, as he was able to frequently use his subconscious, despite his state of imprisonment.
He also gave of his magic to Kitana Kellaway, Doran Purcell, Sean Mackin and Elsie O'Brien, with the latter leaving the group and lamenting her powers. He later controls Silas Nadir into leaving an Echo on Valkyrie Cain, for the sole purpose of dragging her into a parallel dimension, to bring him his "surprise guest".
After Fletcher teleported the Cube to the Accelerator in the Irish Sanctuary, Argeddion, unable to wake himself up from his coma state, controlled the minds of Tyren, Kalvin, Vernon and Lenka for years, and had made them come under his influence, making them generate an impenetrable force field around the Accelerator. This separated them from the other mages and sorcerers intent on shutting the Accelerator down, allowing for nobody to be able to interfere with his awakening.
Argeddion is next seen when Skulduggery and Valkyrie lure him into their presence by confronting Greta. He brings her to safety, then moves right above the Accelerator as Skulduggery instructs. The Accelerator then shoots a beam of magical energy that manages to keep Argeddion in the one spot. However, he summons magic and launches his one beam of energy back through the Accelerator, destroying it and injuring a lot of the mages powering it.
Kitana, Doran, and Sean then attacked Argeddion, in which he seemed to be defeated simply because he did not use any of his magic to defend himself or to attack. The trio then attack the other Mages present around the area.
Kitana then kills Greta when she tries to make them stop attacking him. In his anger and sadness, Argeddion shatters every mental block in the area, including the one he placed around Darquesse in Valkyrie's mind, causing her to escape from the psychic blocks of which he set up within Valkerie's mind. Skulduggery also finds the case with Lord Vile's armour nearby, Argeddion having hidden it in a shed.
Valkyrie and Skulduggery fly back to the Sanctuary, where Kitana, Sean and Doran are attempting to put Argeddion back into the device that held him in a coma, just so they can keep their powers. Valkyrie and Skulduggery attack them as Darquesse and Vile, battering them repeatedly, yet they refuse to stay injured. Valkyrie finds Argeddion feeding them power, but severely reducing his own. Darquesse then starts breaking down Argeddion's defences, but before she quite manages it, Argeddion boots the power of the echo shunt inside Valkyrie. Once in the other dimension, he goes to find his other self.
When Darquesse returns from the other dimension, Argeddion reveals that he has taught his alternate version's true name to him. However, his counterpart refuses to cooperate with his plan, due to living in a world where magic is known to the world, and where the sorcerers are evil, and the weak are kept in rural villages, down in the gutter. When the Alternate Walden tries to force Argeddion to send him back, they have a fight, ending in Argeddion accidentally killing Walden before being knocked unconscious by Skulduggery Pleasant moments later. He is last seen having is memory wiped, and having his true name sealed off to him, in order to be 'reborn' as a mortal.
While he was under the impression that he was a teacher an had no inclination of the magical world (due to Deacon Maybury), Darquesse comes to him pretending to be a friend of some of his students. She breaks down his memory walls by shoving a Remnant in him. When she was done, she rips it out of his throat, killing him.
Argeddion is noted to be a pacifist by many people in the book. Although he has vast magical abilities at his disposal, he has never used them to harm or kill anyone (except for his alternate counterpart, which was purely accidental). However, he has been indirectly responsible for many deaths, as by giving powers to Kitana, Doran, and Sean, he allowed them to go on a killing spree, using his magic to run wild. He also refuses to see anything but good in his actions, and is a little naive, hoping that everyone will share his wish for peace and love.
After discovering his True Name, Argeddion develops unlimited powers. He has the ability to control people, even whilst in a coma. He also had shown the ability to give a portion of his magic to anyone, able to retrieve it when he wished. He even had enough power to destroy a machine channeling dozens of powerful sorcerers' energy, and quickly recover.
After awakening from his coma, Argeddion discovered that he could manipulate any form of magic after experiencing it once. This is true, as he copied Fletcher's Teleportation ability and Silas' Dimensional Shunting after experiencing each technique once.
However, Argeddion did not use his amplified magic abilities for combat, as he was a pacifist. He also showed that he can use his magic to heal himself rapidly, as well as revive the deceased Kitana, Doran and Sean.
Like Darquesse, he has the ability to see magic, and 'other things too' he noted, due to knowing his True Name for a longer period and studying magic more.
After he re-absorbed his own magic from Kitana and her allies even Darquesse admitted that she was no match for some with his power.
Argeddion admitted that if Skulduggery had embraced Lord Vile he may have been able to stop him early in his path to change the world.