Throughout The Trilogy
Arkarian is introduced in Chapter One of The Named, the first book of the trilogy. He is over six hundred years old, but has stopped aging at eighteen. A byproduct of his age, according to him, is the alteration of his original hair and eye color. His hair is thus electric blue, and his eyes, which he thinks were once blue, are violet. Though in the Named, we are told that Lorian, who is revealed to be his father in the Dark, also has violet eyes. Another effect of his youth retention is his inability to live in the mortal world, and although he operates in it for the purposes of the Guard, he does not reside in it.
On earth, Arkarian works in a set of chambers within a mountain (identified by his Apprentice Ethan as being located on "the south-western slopes of the Great Dividing Range"), the entrance to which he can access mentally. Some of the rooms "change often," though it is unclear whether they do so of their own accord or by external influence. The main, octagonal chamber is used for briefings and meetings, and it is fitted with special equipment that allows Arkarian to monitor other time periods, and with them, the Guard's missions - particularly those involving Ethan, and Ethan's later Apprentices.
While in the first book, Arkarian is seen supervising the Guard's missions rather than undertaking them directly, The Dark finds him sent to Medieval France with Isabel, where they are attacked by Lathenia herself. Arkarian manages to fend her off, but she promises they will meet again, turning threat into reality when she has him kidnapped and brought to her in the underworld.
Because of that particular world's danger, Lorian forbids the Guard to launch a rescue attempt. Isabel, whose feelings for Arkarian have grown substantially, ignores the edict and enters the underworld with the help of the Guard's royals. Ethan and her brother Matt go with her, the first out of his loyalty for Arkarian, and the second for Isabel's protection. When the three find Arkarian, he is severely injured, and uses his remaining strength to warn them of Marduke's resurrection. Isabel heals him, but not before Lathenia comes back. Her magician, Keziah, attempts (and fails) to bind Arkarian's powers, which enable him to open the rift between the worlds and thus escape.
After hearing that his rescue violated a direct order from Lorian, Arkarian pleads with Lorian for Isabel's absolution, and asks for his gift of agelessness to be taken away in order to be with her as he found out that Isabel was his soulmate. Lorian exonerates Isabel publicly, telling the Tribunal that his prohibition was a test designed to find the bravest candidate to face the horrors of the underworld, not a testament to Arkarian's expendability. Before ending the trial, Lorian honors Arkarian's request not by stripping him of youth retention, but by giving Isabel the same gift.
In The Key, Arkarian is pushed into the background as the story is told by Matt and Rochelle. His relationship with the former is problematic, as Matt is overprotective of Isabel and distrustful of Arkarian's feelings for her.
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