Terrazine

Terrazine gas is a mysterious potent psionic reagent. It is sought by protoss, zerg and terrans alike. The protoss consider it "the Breath of Creation".

Sources are found on Mar Sara as well as at shrines on Bel'shir, where the protoss gain psionic power.

History
By 2503 the Terran Dominion had acquired and studied terrazine; scientists considered the side effects of terrazine enhancement to be "unpredictable".

Terran Dominion Emperor Arcturus Mengsk and his new adviser, General Horace Warfield, have begun a secret project codenamed Shadow Blade. The program uses terrazine gas to alter the genetic makeup of ghosts. These ghosts are transformed into spectres - shadowy superhuman beings bent on executing the will of their "true master".

Mar Sara featured a Dominion-operated "Vespene" Refinery 1138, a terrazine refinery on Mar Sara, disguised as a vespene refinery, which was infested by zerg and had to be rescued by Nova (a ghost) and other Dominion forces.

Gabriel Tosh hired Raynor's Raiders to retrieve canisters of terrazine from a planet occupied by the Tal'darim, a protoss religious movement.

Terrazine in StarCraft: Ghost
The substance will be explored in StarCraft: Ghost: Spectres.

Terrazine in StarCraft II
Blizzard Entertainment has stated that they are keen on exploring the idea of "this weird new substance" that could affect certain psychic abilities and the spectres, and they might make it into the game. Blizzard employees again said it could be in StarCraft II at New York Comic Con. References to the substance can be found at Blizzard Entertainment's StarCraft II website and in the game itself.