A Living Saint is an extraordinarily devout servant of the Emperor of Mankind, usually a warrior of the Ecclesiarchy, who displays seemingly miraculous, supernatural abilities derived from potent faith in the God-Emperor during his or her lifetime. In almost every case, a Living Saint has been resurrected from the dead, sometimes multiple times. The belief among the faithful of the Imperial Creed is that these individuals are blessed by the Emperor Himself, and are resurrected by His will and grace to defend His servants.
Most of the known Living Saints have been members of the Adepta Sororitas, particularly its Orders Militant, but several have also emerged from the ranks of the Astra Militarum.
In truth, it is clear that Living Saints draw their powers from the Warp much like the servants of Chaos, but are not necessarily psykers during their initial lifetimes. Instead, a Living Saint's faith in the God-Emperor is so great that it allows them to unconsciously draw upon the Warp to fuel supernatural abilities, including the ability to resurrect from death.
