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

When I played this campaign for the second time, I still couldn't get the achievement. I was only able to acquire Dark Magic in the middle of the mission. By the way, it's enough to level up Agrael to level 29. There's a level-up spot somewhere on the map. So, you can get to level 30 easily. However, when I played it the first time, I didn't use this opportunity. I found it when Agrael was already level 30. There are tons of neutral creatures to level up, to suit any taste. You can also send druids from three druid castles to the sacrificial pit. If there wasn't a level 30 limit, Agrael could be leveled up indefinitely.