I'm no supersneak thief, i'm a battlemage, and like to do as much damage as possible. I didn't train and buy all these spells for nothing. Besides, wearing heavy armour doesn't allow me to sneak. I always carry that black light armour with me which you aquire early in the game as a thief or assassin (can't remember where i got it), but i only use that when exploring ruins or caves. Why sneak when you wield Umbra's sword?
