The Story of Brand
Kegan Rodhe was a Freljordian tribesman who, in a moment of desperation during a failed expedition, broke into a vault that legends said contained something dangerous. The legends were accurate. Inside was a prison holding the ancient fire elemental that the Freljord's stories called the Burning Vengeance — a creature of pure fire that had been sealed away by the Three Sisters in an age so distant that most Freljordians remembered it only as myth. The fire consumed Kegan entirely and took his body.
What remains is Brand: the fire elemental using a human body as a vessel and weapon, with Kegan's memories available as reference material but Kegan's personality absent. The thing that calls itself Brand has purposes that predate human civilization — it has grievances against the world from before the Freljord's current tribes existed, and it is pursuing them with the patience of something that has been imprisoned for millennia and is now, finally, free to act.
Its connection to the Freljord's ancient history — specifically to the Three Sisters and the events that produced the world's current magical geography — makes it a threat at a scale that is difficult to assess from the outside. It burns what it touches. It plans in timeframes that make most human scheming look like improvisation. The man it used to be is not gone exactly, but he is not present in any way that matters to Brand's current objectives. Kegan Rodhe was collateral damage in a story much older than he was.