StarCraft/Special structures

Power Generator
After the arrival of the UED to Braxis, their scientists constructed the Power Generators necessary to activate the Psi Disruptor continuously. At the beginning of Episode 6, Kerrigan makes a deal with her Terran comrades, especially Arcturus Mengsk, to lead a contingent of Terran invaders of the Sons of Korhal to destory the Power Generators, thereby enabling Kerrigan to control her minions, which then land on the planet. Subsequently, Kerrigan's Zerg brood destroys the Psi Disruptor so that UED power in the sector is crushed.

Psi Disruptor
Although the Confederacy, when they were in dire trouble from the Zerg infestations, could not find their own Psi Disruptor, which was directed specifically against the aliens, the arrival of the UED resulted in this pivotal structure's resurfacing...on Braxis, a former Protoss colony. Through the rest of Episode 5, the UED Terrans use the Psi Disruptor--despite Duran's attempt to demolish it from within--to weaken the hold of both the Overmind Cocoon growing on Char and Kerrigan the Queen of Blades on their Zerg minions. This quickly led to the Overmind's capture and then drugging by the UED's Medic's Neurostims. Thereafter, the UED power in the sector consolidates.

Ion Cannon
The Confederacy seems in favor of doing too many experiments; one of these falls into the hands of the Sons of Korhal as Raynor's Raiders splinter off from the terrorist organization. It makes a brief appearance in the last level of the Terran Episode 1, in which Raynor and his forces make a daring attack on the Ion Cannon and then flee from the Koprulu Sector.

Overmind
The primary Zerg structure in its hierarchy is the Overmind, which according to lore was created by the Xel'Naga on Zerus but which subsequently moved to Char to direct its campaign against the Terrans. It is the greatest weak point in the Zerg race; if it dies, the war would be over. It DOES get killed by the Warp Blades of the Dark Templar, thus throwing the Zerg into disarray, but not before the Overmind had judiciously metamorphosed a Terran Ghost--Sarah Kerrigan--to act as replacement. In Brood War, then, this Queen of Blades takes control over most of the remaining Zerg.

Cerebrate
The Overmind declares to a Cerebrate at the beginning of Episode 2: