A '''Prognosticar''' is a title and position amongst the ranks of the [[Grey Knights]] [[Chapter]] that consists of powerful specialised [[Psyker]]s. As they are sensitive to the fluctuations to the [[Warp]] which allows them to detect the psychic tremors that are inherent in [[daemon]]ic incursions into realspace. Thus, a Prognosticar is capable of determining the location and severity of such an event. This skill appears similar in manner to an oracle in form though in function is similar to a highly specialised form of hunting instinct. Within the Chapter Augurium, Prognosticars conduct their rituals and meditations in the light of candles where their divinations forewarn the Grey Knights in their deployments.

The current Prognosticar is Brother Hyperiondivinations performed by Prognosticars are extremely taxing and result in their body aging at an accelerated rate. Initiates with the potential to become Prognosticars are very rare. For instance, who served during the [[First War for Armageddon]], only a single Prognosticar, Torcrith, served the order. According This may have contributed to traditionthe Grey Knights' relatively late realisation of the daemonic incursion. Several years after the war, there can [[Hyperion]] - who himself had been considered a potential recruit for the Prognosticars but had been discarded because of his lack of focus - became a new Prognosticar. When Torcrith died a few years later Hyperion in turn became the only be one Prognosticar at a time, and he must select and train his own replacement. ²