"Raistlin"
Anyways, for a materia to do "multiple times the original damage," that means it has to hit more than once. The only materia that do that are: 2x Cut, KotR, Comet, Enemy Skill(some of the spells), and...I think that's it. Oh, maybe Kjata, though that'd be stretching it.
Enemy Skill can do that? If so then I'm pretty sure that's the answer. I though E-Skill but couldn't think of a multiple hit attack, although there is an attack based on original damage.
Big Guard, Death Force and Dragon Force protect you, and it allows you to gain speed during battle by using Big Guard. It also allows you to gain abilities during battle, though that isn't really about magic points.