Quote Originally Posted by Endless Twilight View Post
Mag Elem Nul makes all magic cast by the user non-elemental. It's pretty useless as it makes the -aga spells a weaker version of Flare. Doomsday with Mag Elem Nul is suicide.
Never used it myself, but I assume it could come in handy if you only happen to have learnt Firaga (of the -aga spells) against a fire elemental monster. Other than that though I can't really think of many uses.