When they introduced missions for me, I was already at level 30; if you arrange your deck properly this mission is not a problem. What I do is I build up my army on the field as quickly as possible, I assault the units involved at the top of the screen and absolutely clean house; just decimate all enemy units and claim all regions, then gather my other units except the herald and attack and anhihalate one of the bottom panels. Next turn I move the herald in with Helena and move my allied units all to the other territory (the one with fewer units). Next turn the ones on the bottom regions are regenerated, but the herald and Helena are not moved, as the two surrounding regions are cataclysm'd away. Since you have to take the herald and Helena back to the home panel, in those rounds to get them there you use your other units to annihilate all remaining enemy units. If you do it my way and done right, when you finish the mission you own all regions and there are NO enemy units.
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