[@Crimson Flame]: Well, the solution probably comes from the world itself and how the people within deal with ghosts (because they should exist in a world like this anyways). If the mana in the world prevents him from, say, phasing into the ground or anything else dense with mana, that should work for a start. As for combat utility... I think that making him unable to just phase through magical attacks and forcing him to dodge or just take them head-on should work.