The Scourge buildings can be placed only on dead land, irradiated from the main building and the Ziggurats, which acts like farms and increase army limit. Undead do not have a separate building for towers, but the Ziggurats can be upgraded to towers, which is very handy. The Acolytes build building like Protoss, and the buildings are spread like the Zergs. Other than that, the acolytes can only harvest gold, the lumber is collected by the most simple combat unit. In mission 13, the Scourge advance to the lands of the High Elves.