So I'm training my current character in both destruction and illusion magic. I pretty much stayed away from illusion with my other characters because none of the spells really interested me that much but I thought I might give it a try.

So while fighting a snow bear and getting my ass handed to me (currently level 21) I discovered an incredibly effective and downright dirty spell combination to use against enemies like this. Basically you put a calm spell in one hand, lightning bolt in the other and cast them simultaneously. The nature of lightning bolt is that it hits the target instantly, whereas calm is a projectile that takes a short moment to reach it's target. This means that the lightning bolt will always hit first and the calm spell will always hit second, allowing you to continuously strike the target without worrying about it fighting back. And the duration of the calm spell is sufficient enough for your magicka to fully recharge well before it wears off.

For creatures like this you do need to take a couple of perks in illusion to make your spells effective against higher level enemies. The snow bear is probably one of the strongest enemies this will work against. I guess that means it doesn't completely eliminate the challenge since higher level enemies will always be immune to it's effects.

I used to do something like this on my nightblade. I'd calm the enemy then sneak behind them and assassinate them >.>

It also svcks that you need 90 Illusion for it work on one of the most common enemies in the game (draugr).