The impaler strain of hydralisk were developed on Marek V, which housed Prometheus Company, a Terran Dominion infestation specialist unit. There, Ryloth's Brood was in danger of being wiped out. There were feral impaler colonies nearby (ancestors to the sunken colony) whose essence was used to develop the impaler morph. The impalers were then used to destroy Prometheus Company's base. The lurker was redeveloped on Cavir, a former birthing colony for Daggoth. Kerrigan telepathically seized control of some feral lurkers but was unable to morph additional ones. Abathur determined that the key transformation sequence was missing, and a lurker den was needed. Kerrigan's lurkers found a den soon enough and defended it from the nearby feral zerg until Broodmother Kilysa arrived and reclaimed the den for the Swarm... "Hydralisk Evolution" mission from 'Starcraft 2: Heart of the Swarm' PC game... Gameplay on Normal... ► Watch more Starcraft videos: http://bit.ly/1b1W2yY. Hydralisk Evolution: *Impaler strain: Hydralisks can morph into impalers. Impalers have a long ranged anti-armor attack. Impalers must burrow to attack. *Lurker strain: Hydralisks can morph into lurkers. Lurkers have an anti-light linear area of effect attack. Lurkers must burrow to attack.