The good guy mutant who helped Napeoli and Amber hide

I think the explosion killed him.

We don't really know. Hansel (the mutant) may have died in the explosion, like the other user said, or wandered off to a different part of the mines - after all, he seemed to recognize the danger. The alternate ending implies that Hansel was in on his family's plan all along, but I'm not sure if that ending is even intended to be canon since they chose not to include it.