Minotaurs and Trolls
The Minotaur tribes reminded Karl a lot of the Orcs, in a way. He was using [Brutality] to increase his size and keeping his face covered with a bandana, which was mostly to keep the dust down.
Between that and the hood of the coat that Rae had made him, it was good enough that he didn't need to wear a mask while travelling, and he wouldn't risk being identified.
He wasn't all that worried about being called a human, he had realized that was unlikely to be an issue with the group that they had. But being personally identified was still an issue, if there was someone looking into the dungeon opening.
The increased size actually seemed to set the monsters more at ease than his normal, human size had. It was as if by being visibly inhuman in some way, he was more like them.