The evolution chamber is the result of the Overmind's view that complacency is the road to defeat, causing it to spur zerg evolution constantly. The evolution chamber provides a testing ground for the genetic code of lesser breeds, helping to increase the offensive and defensive capabilities of the zerg ground-based breeds. It is also required in order for a creep colony to mutate into a spore colony.
The base of the evolution chamber forms from the genetic template of an unknown creature. During development, the "chamber" grows around a full skeleton with a skull, spinal column and ribs, that falls apart when the pit is destroyed. The biological roots of this creature is still unknown to terran scientists.
The evolution chamber contains a hardened skin that grants it near immunity to small arms fire, though can still be destroyed through mass C-14 rifle fire. In addition, it possesses genetic transmission appendages that allow it to transmit genetic information to other structures of the hive cluster.
The following section contains information from a previous version of StarCraft which is no longer valid.
Unlike its alpha appearance, the evolution chamber's sprite in the StarCraft beta was mostly identical to its end version, though had a distinctly more withered appearance. In earlier builds of the beta, the evolution chamber's sprite was used for the spore colony and then the fungal colony before ultimately becoming the evolution chamber. In the release version, it retains the placeholder name "cerebrate."