Was able to get to around 40 - I think the implementation is good, and the effects that the enemies gain are interesting, but it can feel bad to have a run full of knights and warriors/beasts and then the enemies gain flying permanently and suddenly you have to replace all the units you spent so long upgrading because they just dont hit the enemies anymore.
I just had a run that I had to sell my 3* beastmaster which felt slightly bad. Maybe these can be a temporary buff? If flying was only going to last a few rounds, its probably not worth it to sell, but I would need to make sure my other units are strong enough to pick up the slack since he cant hit them now, adding some choice there. When the game forces you completely out of melee, that can feel a little dissatisfying.
I hope this doesn't come off as hate! I genuinely am loving this game, and I think it has so much potential, I just want to do my best to help you make it the best it can be. I keep coming back to it and have it bookmarked, you're doing great things with this game! Keep it up (: