Spire

The zerg spire is based on the towering spires of the mantis screamers, although altered to be sustained with creep.

StarCraft
The spire produces the genetic code that allows larvae to morph into mutalisks or split into pairs of scourge. It is capable of mutating into a greater spire after a hive has been developed, enabling the hive cluster to produce guardians and devourers.

Development
During the StarCraft alpha and beta, the spire possessed a different appearance from their final version which had its model borrowed from the scotia, a canceled zerg structure.

StarCraft II
The spire appears in StarCraft II. It functions identically to its predecessor.

The spire can be transformed into a greater spire.

Development
The spire was a simple update of the original game's sprite artwork. The challenging aspect of creating the spire in 3D was conveying the height of the building. StarCraft II has height limitations for building models, especially for multiplayer artwork due to the altitude flying units move at. Buildings exceeding certain heights either require air pathing blockers so flying units don't clip through them, or height adjustments so they're lowered under the flight elevation. Air pathing blockers are not an option for multiplayer art, so the spire was lowered for the sake of functionality. Another consideration was making this building somewhat humble so the presence of a Greater Spire would be more significant.