A capital ship, the tempest was developed by the Protoss after the first phase of the Second Great War, in order to maximize the effectiveness of their war machine against their enemies.
The Tempest is a Protoss capital ship, rivaling the Carrier in size and power. It is designed to handle masses of air units using focused psionic storm technology, but this also makes it an effective ground support unit as well. The Tempest launches an orb of energy with area-of-effect damage at airborne targets, and fires a beam of energy at ground targets.
In the game series, the Tempest is a concept idea for a new class of Protoss capital ships.
For more information see the Tempest on the parent site.