The Templar Caste is a collection of protoss warrior tribes. Descended from great warrior tribes from the Aeon of Strife, these were selected by Khas and his students to act as warriors. The other two castes are the Judicator Caste (leaders) and Khalai Caste (workers).
Templar are trained from youth to harness fear and to give their lives if necessary. Members of the Templar Caste who are particularly skilled psychics are known as high templar. Both High Templar and any member of the Templar Caste are sometimes simply referred to as "Templar".
Before the advent of the Khala, each tribe had a definite proclivity or strength. The dictates of the Khala advised a three caste system, which each tribe fit easily into. The Templar tribes were those who had great physical prowess or agility, or tended towards strategy. In the early days of the Khala, they fought to protect the new protoss culture from those who disagreed with it. When the battles ended, the Templar defended their people from fearsome fauna and later from hostile alien beings while settling their colonies. Even in times of peace, rare as they were, Templar would train constantly. Before the Fall of Aiur, members of the Templar Caste would often make pilgrimages to various sacred sites on the planet.
In the early phases of the Great War, the Templar deployed the Koprulu Expeditionary Force to combat the zerg infestation on the terran worlds. After the fighting on the terran worlds abated, the fleet's commander, Executor Tassadar, opted to follow the zerg to Char rather than return to Aiur taking only his command ship with him.
The Templar were engaged during the zerg invasion of Aiur. Uninspiring leadership by the Conclave hampered their efforts. Further difficulties arose with the return of Tassadar and the short lived civil war which further divided the Templar's resources. Ultimately the battle was lost and the Khalai were forced to abandon Aiur for Shakuras.
During the Brood War many Templar rallied to Judicator Aldaris in an abortive uprising against Matriarch Raszagal. In the years after the conflict, the Templar often called for a return to Aiur. In 2502, the Templar were quick to respond to resurgent zerg activity in the Koprulu Sector. They secured the xel'naga temple on Artika from the Terran Dominion and the zerg Swarm.