Enemy Within

Enemy Within is a mission in StarCraft II: Heart of the Swarm. It is one of only two missions where Kerrigan is not playable at all, though her instructions are heard throughout.

The Mission
A single protoss vessel managed to escape the Swarm's wrath.

Sarah Kerrigan implanted captive protoss Lessara with a special larva, then allowed the protoss to warp Lessara back to their vessel. The larva emerged, and, evading detection, began to infest creatures on the vessel.

Eventually it becomes a broodmother, which tried but failed to make contact with Kerrigan.

The protoss crew is eventually destroyed, and the zerg infest the entire ship.

Secret Area
After the player has destroyed the warp core and completed the timed objective, an area towards the bottom left of the screen becomes available. The room appears to be a protoss kitchen. A can of Pylon Poweraid is available next to what appears to be a counter. The Poweraid is solely aesthetic but can be selected for Easter egg quotes.