Sunken colony

The Sunken Colony is the Zerg's only static means of ground defense. Using deadly Subterranean Tentacles to surprise and puncture enemy ground based units, the Sunken Colony can quickly turn the tide of a battle. The best use of the Sunken Colony lies in building them in clusters and using them in conjunction with Spore Colonies since they have no detection abilities of their own and would be unable to defend against cloaked, flying or burrowed units. Due to its high cooldown, the Sunken Colony is vulnerable to swarming units such as Zerglings or Zealots.

Notably, the Sunken Colony is the only static defensive structure to deal explosive damage to ground units. While Sunken Colonies do 20 points of damage to small units (like the Photon Cannon) the Sunken Colony is very useful late game, because it may do 40 points of damage to Large class units (while the Photon Cannon will not).