[quote=@Rilla]
Where would he get the mana, or whatever he'd have to use, to use his magic? 
[/quote]

The idea would be that 

1. He has one mana 'potion' for each fight he enters, which is difficult to administer, and takes some time to kick in. To add another limitation that T1 somewhat overlooks, it will also burn out quickly if unused, so he can't just administer it immediately and walk around like a primed crossbow. (analogy is bad)
2. In a continuum his world would meld into the continuum, making very rare pockets of pure mana he could harvest for new potions.
3. Blood magic, basically.

Also, mana will be linked to his ongoing battle with both black mana corruption and ageing, making him something of a mana addict. I'll be retiring Isaac the ghoul because of this similarity, though the difference is between extreme physical capabilities and extreme magical capabilities.