Brodgar was born the son of a Jarl, far enough down the line of succession that turning to the church was an obvious choice. He served faithfully as an acolyte and was a considerable prospect for the Inquisition. To all who knew him, he seemed a respectable and pious dwarf.
Which is why it came as such a shock when he struck a guard captain.
Having needed someone to blame for a localized insurrection, the captain had drug out, beaten, and humiliated a local wizard, and in front of his family. The charges were trumped up on scant evidence, and Brodgar, having been attached to the unit for arms training, saw it as the last straw. More shocking than his brash assault was the impassioned speech he gave about the lot of humans, free will, and the place of dwarves in Baal's plan.
The charges were quickly upgraded to heresy and, thanks to his station, the sentence was merely expulsion rather than the usual execution.
Other thoughts/topics:
What exactly does being 'expelled' mean? From the lands of the Jarl? From the Iron Marches? If he shows his face in Baal-controlled lands, will he be known as a heretic or merely a prince-in-exile type?
Related to that, thinking he may be physically branded in some way (mostly as a cosmetic feature)
Need to touch on his personality/beliefs instead of just backstory.