The most UNPOPULAR faction in Heroes 5.

The units for mages are good. I don't like the hero's overall development. The damage is less than that of dwarves because the attack tends towards 0, and the defense is also poor, with a low chance of gaining combat skills... And the magical power isn't outstanding enough to compensate with magic, and there's too much mana – you won't spend that much. BUT... when the mage develops... In principle, you can capture cities using only gargoyles equipped with mini-artifacts (+7 health, +11 defense – quite achievable, magic doesn't work...). And kill enemies with Phoenixes and elementals...
There's also another option – I, for example, enjoyed playing as a demon hero for the mages.