using magic eyeFirst of all, it infuriates the oposition, just to see your leacherous item stuck on a creature under their control.
It's main use though is to drop on enemy creatures and keep track of them. So the obvious target is an enemy wizard - if you can get close enough to drop it on an enemy spellcaster. From that point on (magic eye doesn't wear off!) even if the enemy wizard teleports or makes itself invisible, you'll always know where it is. Very useful info that is too.