The Original Agent Mantis was lost when he volunteered to explore a man-mad pocket dimension to aid in a government research project.
The superimposed extra dimensional layers collapsed on themselves effectively erasing him from existence. All that was recovered was his mask, fundamentally altered from it’s previous state. It was now composed of self-isolated antimatter particles that had the researchers mystified. However there was more to this Anti-Mask than their instruments could detect. Something wicked had imprinted onto it, and anyone who might wear it.