Magic—it was something that Raze originally thought he was the only one who knew about in the World of Pagna, and so he believed it was his trump card. He would use his knowledge to get ahead of others and create items that would help him along the way.
He soon found out, due to the organization Alter, that this wasn't the case, but he still had an advantage. He wasn't just any mage; he was the Dark Magus, a nine-star mage. Something that could only be counted on one hand; so few had achieved such a feat.
Still, it was something he needed to build from the ground up in his new body, and due to his infamy, it was something he still needed to keep secret from the rest of the mages in Pagna.
At least, keeping everyone thinking that the Pagna warrior Raze Cromwell and the Dark Magus were two separate people.