Need help with a spell

I'm making a new map and there's a hero in it called the Mage Knight who I want to give a spell sorta like mana shield. However, Mana shield can obly absorb a maximum of 10 damage per point of mana, which doesn't do very well, especially since the spell goes up to level ten and things do a lot of damage...
However, I went and played this game called Enfos Hero Survival and there was a hero called the mentalist who had a spell called aura of deflection that reduced damage taken by a certain percentage and drained a set amount of mana per hit and had the animations for mana shield. This is just the kind of spell I'd like to have, but I don't know how what spell to base it off of, or if it's a trigger spell. I thought maybe it was based off defend and added a mana cost and such... but I don't think that'd work, plus I think you can only reduce piercing and magic type damage with defend. if anyone has any ideas, please help me out :-D:D

bump

hold down ctrl... or shift... (can't remember) to remove the world-editor limits when editing something.... think that would work.

The word "impossible" comes to mind.......

Enfo's Team Survival does use the basic mana shield. At level 10, it absorbs 100% damage and uses 10 "Mana per Hit Point" (I've never liked the way that they phrase that). Anyways, if you play long enough, you'll see how awful it is in the later levels.