Also, sorry about not posting at all as of recent; school bit me in the ass, and my procrastination has begun to catch up with me. I'll try to make my post when available. But a new person should add some new interest.
Not particularly, though, they tend to be regular moves, just with about 70 power, 100 accuracy, and the benefit of almost never being 'not very effective'. NOTE: you cannot get STAB (Same-type attack bonus) from void moves.
Nope. Unlike shadow moves (which were used in the previous battle by both Desia and Quartzil), void moves are only normally effective against every typical pokemon type... obviously, they're exclusive to void pokemon... one of which happens to be the main character. (hence the immunity to shadow moves and the discoloration)