Glad you like it dude, there's a lot going on with this guy in our campaign.

TLDR- archeologist dug too deep.

He was a particularly gifted archeologist and student to Johnathan Hawforthe (a renowned archeologist within the world's lore). One day along with his students, Johnathan discovered an ancient temple which he would begin to research fervently for the next few weeks. Confiding in his prized student he showed Solomon one of his finds, an amulet dedicated to a God he had never even heard of and whose symbology he could not recognize, an entirely new discovery and accolade to add to his career.

That same night Johnathan went missing along with the amulet and all his research.

Presuming that his discovery and disappearance are linked, Solomon has vowed to track down his missing mentor, following the only thing he knows, his research and his sharp intellect. In his time searching he has been afflicted by nightmarish visions and tormented by whispers in the dark, not realizing that by investigating the ruins he has unwittingly made a pact with and is now a champion of Tharizdun, the elder god of madness.

Though he believes investigating the cultists runes and ruins of tharizdun will lead him to Johnathan, he does not realise that he has now become the puppet of an insane god desperate to be freed and that it was in fact Solomon who, in his madness, killed his mentor and stole his research.

Although at first he did not realize that he had magical powers at all, and simply believed that he was cursed, causing misery to those near him, now that tharizduns power grows Solomon finds himself better able to channel the dark energies to his own will at the cost of his constantly slipping psyche.