Arctic Zerg Ultralisks are more than just snow-affiliated weird looking Zerg Ultralisks. They literally are a walking spotlights, pointing its allies where enemies are hiding.

Arctic Zerg Queens are in some sense link between structures and units as like Zerg Crawlers, Arctic Zerg Queens are capable of switching between stationary and mobile modes. When on mobile they can freeze the enemy structures and make them unfuctional this way, without direct destruction as usual. When on stationary, they can protect the Zerg Hive Clusters by freezing down an attackers.

(Zerg Ultralisk and Zerg Queen belongs to Blizzard)