Heart of the Swarm Campaign- Skygeirr: Infested (Part 3)

The first of these is located near your prime secondary base location and the next Terran major base, in the Northeast corner of the map.  You'll need the support from the infested Terran troops to clear out this base, so wait for the gas to die down and build up your defenses and assault force before moving against it.  The base is small and thankfully produces no troops.  It unfortunately also has nothing for you to infest aside from some SCVs, which are really only worth it for a bit of a giggle- they don't actually let you build Terran structures or even infested command centers, more's the pity.

Immediately to the West of that is a small 'peninsula' housing several ghosts equipped with a nuke or two as well as some predators and a larger garrison- take care when going after this virophage location, as the nukes will devastate pretty much anything you can field.  Further to the Southwest is the second science facility, in a rather inconvenient location far from any virophage by land travel- which is how you need to reach it since it's creep tumors that will take them over, rather than infestors.  Up a hill to the Southwest is another large Terran base with two more garrisons in it, one near the slope and the other in the far Southwest.  This base holds a few thors, as does the small 'peninsula' to the Northwest of it where the third science facility is located.  Take care when trying to collect these goalpoints, as it's easy to accidentally just not see two of the thors where they wait by the science facility, and they'll happily take out your virophage(s) for you while your troops are distracted elsewhere.

During the third bout of anti-infested gas, the Terran forces will extend a bridge across the central space from the Northwest to the Southeast right by the third virophage and your main base.  Be wary of this- it gives them a shortcut straight to a virophage and if you don't cut them off hard, they'll slip some troops through either by medevac or just walking.