Ataman
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Just kidding. You leave your army there, except for the wolf, which doesn't have a movement penalty on stones, you free Dessa from the dungeon, and you have enough turns to return to the Fortress, using one fly spell to take out thirty griffons with magic... We lose Fiura, but then Dessa takes the Fortress without losses... almost... :)
P.S. How many units did everyone save in the battle with the Archangels? I saved 2 Dragons and one Griffin.