Heart of the Swarm Campaign: Kaldir- Enemy Within

With the Protoss colonists launching an interstellar ship formerly hidden behind Kaldir's moon, Sarah is going to have to take some extreme measures to prevent the Golden Fleet from coming and striking not only her Zerg forces, but also the former Queen of Blades herself.  To that end, she intends to use the Protoss colonist that was captured during an earlier mission on Kaldir.

Completing this mission will give you access to the evolution mission for the roach unit, and completing the bonus objective will give Kerrigan an additional level.

The mission itself opens on the Protoss ship, with the death of the parasite-infested colonist.  You are given control of a single larva, parted from the Protoss woman it was implanted in, and must have it skulk and infest until you can gather the bio-matter needed to kill the colonists and take control of the ship.

To the Southeast of the insertion point, you can find the first of several curious 'doors'- the Protoss apparently use massive cylinders that retract into the floor to close off one part of the ship from another, rather than simple, thin chunks of metal.  Kerrigan will remark that there is a lot of bio-matter to be found here, which should be used to further the larva's growth.

Past the large door, you wil find the first useful target- a quadruped of some sort.  The larva's Parasitic Invasion ability will allow it to leap into the creature and gain control of it.  You must do so quickly, so as to be concealed from the zealot that approaches from the Northeast.  Wait for him to move past, and you can use the Consume power to kill the lyote and collect its bio-matter for the larva.

Moving on to the Northeast, you will spot a sentry- Sarah instructs the larva to hide in the nearby steam vents until it has passed.  It will still be able to see the larva when it leaves the steam vents, so accept that you're going to have to deal with some damage- just rush for the steam vents further to the Northeast.  Once the larva is within that area, the sentry will lose track of it again, and cease firing.  You must then wait for the sentry to depart once more.

Another set of steam vents waits to the Northwest.  Head straight for these so as to maintain cover, and the larva will gain sight of a much larger creature- a Giant Ursadon.  There are several zealots nearby as well, who you are going to need to kill.  Thankfully the ursadon can attack, unlike the lyote.