Worshipper – “Conquest” [Campaign 2, Mission 3]

The first time, I probably struggled with this mission for a week. I complete it like this: In the demonic castle, I don't build anything; I immediately attack Gilraen with what I have. He usually flees, I capture the lower castle, the mines, and develop. By the way, if you're playing the non-gold version, the lower city isn't fully built, and I wait for Gilraen to leave. As soon as he leaves, I buy all the elven troops. If there are any demonic troops left, I disband them because, in the non-gold version, there's a feature where Gilraen doesn't capture your city if there's no garrison. I move away from him. He goes one way, and I go another. I go up through the river; if I make it in time, I capture the city; if not, I just go along the river to the center of druidic magic, destroy it. Gilraen can't attack you there; it's like a sanctuary, he doesn't see you and leaves.