The battles are situated in an arena. Its to be taken place in the arena. This building, the cathedral, is just an add on to the arena. You can't necessarily leave the arena. What would stop someone who can fly from flying away when wounded to return later at full health. If kuja brings down the cathedral, in which the cathedrals base is the size of the arena, raziel has no where else to enter the material realm. He affectivly be stuck there, unless you make a rule that states an opponent can leave the arena, and come back at a later time. Because i know he can rematrialize at a shift point thats not obstructed by stuff OUTSIDE of the arena. SO raz, tell me what this other way of switching realm's is, because Raziel is gonna need it.