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A solid, powerful map!
I played through it in 8 months, and they gave me awesome dogs as a reward for completing it. The final castle is very overpowered! I could only defeat it with dark magic and by trapping it in the castle; the battle lasted about 25 minutes! There are, of course, a lot of units, and they keep multiplying.
Is the quest to kill the last gnome supposed to be uncompletable? It's unclear...
I spent a lot of time clearing rubble.
Also, after capturing a garrison, the caravan from it wouldn't reach the castle – it would disappear near the rubble; this is a bug.
It's probably a bug, or maybe you just didn't notice that the caravan was reaching its destination.
But it took you 8 months. Naturally, the army will be large.