@Creed Angelus; thats just my opinion. You prefer watermalon's one, I do like mckill2009 entry.
Don't force me to change my decision in case everyone has it's own criteria.
And sorry - you say illusions trick enemies
I say: Those illusions have just one order, when player who controls a hero orders him to do anything else.. you must be blind to not realize which unit is the correct one.. where the trick? ;/
Well, nope, I'm not convincing you to change your idea.
Exactly why I said "personal interpretation."
And for where's the trick...
Ok, so if this skill wants to trick an enemy, it has to be used by a hero with mostly passive abilities. (Critical strikes, stat bonuses, orb effects...)
Let's say the first time the spell was used, it was aimed at the ground. The user turns invisible, and leaves the enemy to deal with illusions. The number of illusions automatically confuses the enemy, and may get him to cast his spells. If he does, and realizes that they are all illusions, he will have been tricked into spending mana for nothing.
Now let's say the second time it was used, it was aimed straight at the target unit. This time, the caster is among the illusions. If the enemy has learned from the first time this was cast, he will expect all the units around him to be illusions. If he shrugs them off, thinking that, he has been tricked into taking a decent number of attacks from the illusionist.
The enemy would then learn from the second cast, and by the third time the caster does it, the enemy will be unsure of what to do when the illusions come running in.
Side note rant: Remind me again why this argument started? Mehehehe... Again, I'm not convincing you... Just stating my mind.