D12, and what difficulty level were you playing on? I played as the Warrior, so it seemed way too simple to me:( Nobody sailed toward me, so I had to sail down myself; there, on one side, there were maybe 200 Paladins (near Novostrozhinsk), and from the direction of Mythograd - Death Knights, also probably more than 200. Well, I entered from the horse side, smacked them, and captured the city. Halfway to Mythograd, I met their hero with a very modest army and wiped him out in one go. In Mythograd, a bunch of zombies were waiting for me, and that was it...

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By the way, I was sailing at the beginning of the mission too, because I completely forgot that I had played as Necromancer on this same map. I was so surprised when I found Mythograd:o In short, no one ever boarded my ships.