Board Thread:Speculation House/@comment-6500074-20130828124819/@comment-17720343-20130828161627

As for the mask, I have a theory that it is similar to the vizored/arrancar masks from bleach. either he was human and somehow gained access to the powers of grim, granting him great power at the cost of damage to his sanity, or that he was once a grim, either originally or human turned grim (if thats possible, we dont really know yet), and the mask 'seals' him grim side, but his dark side's personality is leaking through, accounting for his amorality with regards to the crew members of that train's lives.