But taking such a weak hero is pointless.
Sylvan units are very dangerous in Heroes of Might and Magic III, but these are useless.
Advanced Chaos, level 7, 255 damage from 6 level 7 creatures?
At least give him Titanium Lightning and expertise in everything else, ideally also Wave of Fire and Chain Lightning; with the current parameters, he won't be worth anything.
And what do you get in exchange for Mirror Image? Is it Anti-Magic?
Added after 33 minutes
if he's level 7, then maybe, but they'll lose a 30/30 or 50/50 battle against Archangels, Devils, and others; a stack of 50 is useless. It's just a weak guard that deals a little magic damage. According to the table from Heroes of Might and Magic III, there's a minimum damage increase of 50 per creature; how can you achieve that with standard spells, when the magic power is calculated in a stupid way for creatures, and Chaos/damage simply loses its meaning at medium quantities... Even a level 7 hero with Titanium Lightning is much more dangerous than with this "set."