Necromancer – “Invasion” [Campaign 3, Mission 3]

Remove the mod and try playing again.
Due to a script error, anything could have happened.

I'll try playing again, but this time I'll make sure that only unupgraded skeletons join, and so on. If Cyrus appears, I'll run away, lol. But I wouldn't want to remove the mod right now because I haven't finished a few single-player maps where heroes from the campaigns are used, like Kujin, Arantir, and Ornella. If it doesn't help, I'll remove it.