Lurker den

The lurker den was a zerg structure set to appear in StarCraft II. It was evolved from the hydralisk den and was required for the development of lurkers. It was canceled by the beta as the lurker had been removed. However, it is still in the map editor.

It was referred to as a lurker den in February 2009; it was previously known as the deep warren.

It used to have a "cool" morph animation, but it was lost during development. The morph animation is still in the map editor. The lurker den (and its morph from hydralisk den) are available if playing as zerg on the custom map "Vulture Nest".

Evolutions
The lurker den enabled the transformation of hydralisks into lurkers.

Heart of the Swarm
Heart of the Swarm beta files indicate that the lurker den will appear in the game, as the impaler den is listed as an upgrade of it. In the retail version, the lurker den and the impaler den ended up being variants of the hydralisk den unlocked based on the player's choice in the Hydralisk Evolution mission.