Thorne’s betrayal and his role in the plot are spoilers. Reveal only if you’ve started the game or don’t mind knowing.
Thorne is a bat and the principal antagonist of Mina the Hollower. He served as the former head of Baron Lionel’s guard — one of the Baron’s closest allies — before he turned against him. Alongside his shock troopers, Thorne destroyed the Spark Generators, plunging Tenebrous Isle into darkness, flooding it with monsters, and setting the entire story in motion.

He is the face Mina is chasing for most of the game. He’s also the first major boss you fight — see How to Beat Thorne for the trident, bomb-trail and tornado strategy. Crucially, he does not die in that opening encounter; he flees on the brink of death, leaving his true purpose a mystery.
That mystery is deliberate. The story is built to make Thorne look like the obvious villain — and reviewers have noted it then subverts exactly that read, building toward a major end-game choice that “determines the fate of just about everything.” For more, see the Story & Ending Explained page.