Dragoon pilots were generally grievously wounded veteran templars retrieved from the battlefield. On occasion able templar would become pilots.
Selected protoss were transplanted into the exoskeleton's core. By the time of the Great War the core was a fluid container and the pilot was submerged within. Catastrophic damage frequently resulted in the tank being breached and the contents spilling out. The pilot's mind interfaced directly with the machine through mysterious essence translators with the use of the Khala. The end result was that pilots controlled their exoskeletons as a natural extension of their bodies.
The dragoon's phase disruptor fired antimatter bolts sheathed in psychically charged fields. A similar weapon was used by the photon cannon.. The quadrupedal walker moved efficiently over unstable terrain.
A sacred shrine on Aiur was dedicated to the creation and maintenance of dragoons. The pilots were honored in protoss society but their status sometimes marked them as outsiders. The loss of the shrine after the Great War made it difficult to create new dragoons. In the interim the surviving dragoons were upgraded into immortals to preserve their numbers.
The dragoon interested other parties beyond the Khalai. The Dark Templar stalker was inspired by the dragoon. As with other protoss technology, terran groups conducted research into the mechanics of the dragoon. The Kimeran Pirates stole (among other things) a data file titled "Utilizing Dragoon Technology For Human Reconstruction" from a Confederate remnant installation following the Brood War.
Historically, crippled veteran templar could volunteer to continue serving by being transplanted into dragoon exoskeletons. This honored tradition was broken when the zerg infested the sacred shrine dedicated to the creation of dragoons during the fall of Aiur. After the Brood War crippled protoss soldiers were transplanted into the new immortal shells. The remaining dragoons were transformed into immortals as well.
Immortals are outfitted with twin phase disruptors as their primary attack form; they give critical fire support to legions of zealots against ground targets. Their specially hardened energy shields only activate when struck by powerful attacks, which leaves them more vulnerable to the pinprick attacks of lesser foes.
The Dark Templar are masters of stealth and guile, though the fall of Aiur to the zerg demonstrated that guile alone cannot defeat a foe as relentless as the Swarm. Inspired by the ancient and honored dragoon walkers the Dark Templar have begun to build war machines of their own. The stalker is a machine controlled by the shadow-essence of a Dark Templar warrior fused into a metal body.
Swift and deadly, stalkers have been credited with many fantastic powers in recent conflicts. Nevertheless the only one that has been witnessed consistently is the ability to instantly teleport or "blink" from one spot to another. This ability enables stalkers to strike from unexpected quarters, catch a fleeing foe, or escape an unfavorable encounter. In addition, the deadly particle disruptors mounted on the stalker's carapace are adept at crippling both ground and air targets. Ambushes by groups of stalkers have brought fiery doom upon many attack wings that thought themselves safe from retribution.