[DGDobrev]

Well, actually it is not a bug. If you are referring to the groups of enemies that are protecting the maps, they are supposed to be much, much harder to kill and may give you bonkers until you find a way to defeat them - especially if you're trying to do it without losses, like myself (at least till I get 50 no-loss battles).

What I can propose is to clear out everything else on the island but the map defenders, go to the next island (Bolo) and try to kill something there, gain a few levels, probably re-make the army and try again.

If you're playing a mage on impossible, you should also be aware that she has the hardest and the most challenging start of the game.

EDIT: I have discovered that especially on impossible, having extra leadership is extremely important in the beginning. When making the game, try to get a few + leadership items at start. There is also a chance you will get a simple +100 leadership belt in the training battles. I consider it a good start of the game if I find the marshal's batton on of the first island and the +100 leadership belt in the training battles, because I know that I can afford it (8000 gold) with any char after I've cleared out most of the island.

On lower difficulties, you can do with pretty much everything, but impossible provides a bigger challenge and one must adequately prepare for it.