Generally, it’s best to specify the location. There are maps where you can reach another player’s Castle in a week. As for where such an army came from, you can only guess. Neutral creatures might have joined. However, they never joined me unless I had a strength advantage. It could also be due to a mod. For example, a mod that allows you to recruit heroes from campaigns. A legion of dragons would join Marcell with just one skeleton, not just units of level 4 or 5. Another possibility is that in the scenario, the Castle at the start might not be level 1. The game is a licensed version, without any mods or updates. The Castles only have a tavern. I don’t remember which maps it was (it was mentioned twice), but they were from the Hammers of Fate expansion. They were probably large maps because we were playing with two players.