Worshipper – “Ship” [Campaign 2, Mission 4]

I don't know about you, but I played it like this: I simply captured the city in the center at the bottom (Elves), then went down into the underground and built up my Elf army. I cleared out two garrisons and approached the Northern Fortress, and with the help of magic, I sent troops there every day and won, using the auto-battle feature!