Well that depends on what your going on. Each magic has been explained and used in a lot of different ways. And you can't have a divine priest because that title would be offensive to them. Also that divine magic is learned to the Paladins of the order. Though holy and divine are technically the same, they are more like to different styles. Celestial magic just depends on what you prefer since it has been changed in its meanings a lot but most times it is referred to as summoning special spirits.