Gatekeys are key-shaped crystal devices used by Protoss to control portal structures (Hot Wheels - Battle Force 5: Battle Key). After the disastrous effects of leaving the Warp Gate open during the Zerg invasion of Aiur, Protoss scientists set to work on countermeasures against future incursions. To prevent these countermeasures from harming their own kind, Gatekeys were created alongside them. Some Gatekeys can be programed to control Stone and Crystal Guardians if present to defend the Gateway/Stargate from invaders (Transformers: Key to Vector Sigma).