Sounds interesting. I can definitely imagine about a minotaur running accross the battlefield, trampling his enemies, and meanwhile chopping some heads off with his axe.
"Training is principally an act of faith. The athlete must believe in its efficacy: he must believe that through training he will become fitter and stronger, that by constant repetition of the same movements he will become more skillful."
I'm not sure trampling is that great at the moment, in most cases.
It might be too good for some units but they could be given weaker attacks or something.
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Great indebtedness does not make men grateful, but vengeful; and if a little charity is not forgotten, it turns into a gnawing worm.
I think that the problem is not about units with the trampling ability (who could always be tweaked a little to balance up if necessary) but for heroes who gain it through an item. If Boots of the Behemoth gave you trample without affecting any of your existing attacks they'd be a real no-brainer. At the moment it's often a tough choice depending on the opponents you face.
Maybe there should be a penalty to attack skill to represent tripping over all those little bodies...