Bug in campaign 3, mission 3, when playing as the Necromancer.

Probably this will be an outdated post now, but the problem is with the mod Maps_ToE_UnlockAllHeroes.h5u, which unlocks all heroes available in the original game for recruitment. Delete it, and the problem will be solved (mission 4 also doesn't work because of this mod). Gold Edition? That's a pirated version packed with old mods, like Minotaurs without helmets, beta Ents, and Dark Elf Riders. It would be better to download a clean version.