Scared man trying to make his way in the world without causing too much of a stir.

As Callisto tells it, he grew up in a small, unassuming town near the Baerwood, and lived a small, unassuming life for some time. He grew up and learned an amount of magic but ultimately he was a wanderer, travelling across the world and seeing the sights. He even saw the Gloamwood when it was all just Arboria, and the dark elves were but a thing of the future. As he has remarked upon in the past, he has outlived all of his friends, and because of that he tends to keep his head down, joining the Tenebric Vanguard shortly after the Night of Dark Tears and a number of his close friends deaths in the hopes of finding a place to keep his head down until the end days came.
 
However, the reality of the situation is much more dire. Callisto harbors a darkness inside of him: once serving as the High Nephilim of the Omniscient Dawn, he could be held accountable for any number of wartime attrocities carried out in the name of preserving the peace and ensuring the gods remained on their thrones, despite the efforts of the Pathfinders. However, he is on a quest of attonement. After being used by the Order and manipulated into becoming the Vessel for the Dark, he fought the Wanderer on the Night of Silver Tears, and at the Dark's defeat, he was cursed to become its prison. The Wanderer spared him for the soul purpose of containing the Dark within him.
 
Now he is a Lord Flamebringer and is on a journey to become someone worth sparing.