As for why Bruce looked at that thing with a strange expression, it's because that was his foolish brother Alvin.
Back then, those cultists relied on Alvin to infiltrate, originally planning to use him to control Bastia, but clearly, he was a foolish ally, bringing doom to anyone who teamed up with him.
On an impulse, he killed the Earl, catching not only Bruce and his group off guard but also the cultists, leading to the ensuing chaos.
Afterwards, it was evident that the leader didn't spare him, and useless Alvin was twisted into a monster.
If not for the lingering glimpse of his face, it would have been unrecognizable, and even as a monster, he was quickly killed, by Bruce's own hands no less.
However, without much hesitation, Bruce swung his sword down, severing the monster's dried head and carried it in hand, walking towards the castle.
