They did say previously that the facility they are fighting in (the arena) was engineered by their kin (+ the whole metal manipulation thing) so I guess that's how the Pixi destroyed his???
Also it has been mentioned that the MC is wearing a collar of much stronger species, which is why the collar is much stronger then the one the Pixis had
Why can the Pixi destroy his inhibitor but our guy can't? I mean it seems a higher grade one but come on. I mean the reason is plot but still