Here’s some Stone Lore, or mostly just what he is, he is a Mineralis, a species in his dimension that has a layer of either Minerals, rocks, or ore, protecting their flesh, Now they cant exactly turn anything into what their layer is, Stone can do that as a form of experiments to become stronger, he
Used it to Kill anyone who stood in his way but as he killed more and more people, his powers started to weaken, so he created his 2 pronged pitchfork lookin-saber so he doesnt use his powers as much anymore.

(Yes i made this up along the way and yes, you can be critics over it, i dont really care)