Host is choosing between swarm or wave mode
My units are under attack by a large zerg force here. There are lava scorpions which shoot fireballs, lava roaches which tank fairly well, and hellspawn which are zerglings.
You can see the mothership's units and abilities here
A disruptor is using a stasis field in this image which slows down all enemy units caught in its matrix to a crawl
You can see some lava roaches attacking zealots and stalkers here