Sentry

The sentry is a protoss combat drone built to support frontline warriors at a time when the protoss race could no longer afford to spend lives freely. Conceived to shore up the dwindling ranks of the zealots it accompanies, the sentry hovers above the battlefield on generators that create pockets of zero gravity, and it fights less by destroying than by shaping the terrain of combat itself. Its weapons are woven light: force fields that wall off advancing enemies, guardian shields that blunt incoming fire, and hallucinations that turn a small strike force into the illusion of a great one.

A drone for a dwindling people#

The sentry was created to address a hard truth of the protoss condition: their numbers were diminishing, and every warrior lost was a loss the race could ill afford. Rather than field still more living soldiers, the protoss built combat drones that could stand beside the zealots and shield them, multiplying the effectiveness of a smaller force. The sentry levitates above the ground on generators that produce pockets of zero gravity, keeping it mobile across terrain that would slow a walker. It carries a disruption beam for direct attack, but its purpose was never to serve as a frontline fighter. It exists to keep the warriors around it alive.

Light woven into walls and shields#

The sentry's defining capability is the manipulation of light into semi-solid forms. Using a light-weaving force field generator, it can transform bursts of energy into small, impenetrable barriers, dropping them across a battlefield to hinder, block, or funnel the advance of enemy troops. Ordinary soldiers and vehicles caught against these translucent walls become easy targets for protoss ranged weapons, though creatures and machines of prodigious size can shatter the fields' cohesion and break through.

By the same craft the sentry raises a guardian shield, weaving light into a semi-solid state to surround itself with an area-encompassing barrier that safeguards nearby protoss ground forces. Projectiles or energy blasts that penetrate the field lose part of their kinetic or thermal energy and a measure of their effectiveness. Because the shield covers a considerable radius, it is not strong enough to make much difference against the largest ordnance, but it meaningfully extends the survival of the warriors it covers against lighter fire.

The art of the false army#

A sentry also carries an in-built holo-projector capable of creating hallucinatory images composed of solid light. These holograms are three-dimensional and can mimic protoss warriors, vehicles, and constructs, and though each replica lasts only a limited time, it can withstand some degree of punishment before failing. Their purpose is twofold. They draw enemy fire while a real strike force maneuvers into position to deliver a killing blow, and they make the enemies of the protoss believe they face a far larger force than the one truly arrayed against them. In both cases the effect is the same as the sentry's other gifts: protoss lives preserved.

Adoption across the factions#

By 2506, some sentries were outfitted with portable shield batteries so they could better sustain the lives of protoss warriors in the field. The design spread well beyond its makers. The Tal'darim had incorporated sentries into their arsenal by 2504, and by the End War they had developed their own variant, though some were left mostly unchanged to provide a varied array of robotic support and a degree of misdirection. Many Purifiers retained sentries even though they normally deployed energizers, while the Ihan-rii powered theirs with volatile xel'naga relics known as nebula wells. After the End War, as part of an artistic movement recalling the Golden Age of Expansion, some sentries were redesigned in the ancient styles of that era to complement vessels with longer histories.