The zerghydralisk den bears only a passing resemblance to the nests of the once peaceful slothien that the hydralisks evolved from. Containing hydralisk genetics, the structure allows larvae to morph into hydralisks.
The hydralisk den and hydralisk strains are exclusive to Kerrigan in Co-op Missions. Kerrigan also has access to the lurker and lurker den. Additional upgrades for the hydralisk and lurker become available when Kerrigan reaches Level 6.
The following section contains information from a previous version of StarCraft II which is no longer valid.
The hydralisk den was a straightforward revamp of the den from the previous game. Nothing significant happened after the initial creation aside from a texture pass and the addition of more little spikes to match the other buildings.