St. Basil received a vision of the Theotokos (the Virgin Mary) to travel to Georgia to censure the King and his court for their profligate lifestyle (in his youth, Demetre took more than one wife). The saint appeared in court and implored the king and his court to turn away from their lifestyle. When they dismissed St. Basil, he was impelled to respond with this prophecy:
A vicious enemy will kill you, and your kingdom will remain without refuge. Your children will be scattered, your kingdom conquered, and all your wealth seized. Know that, according to the will of the Most Holy Theotokos, everything I have told you will come to pass unless you repent and turn from this way of life. Now I will depart from you in peace.
At the time, Georgia was a client state of the Ilkanid Mongols under Abaqa Khan, who died in 1282. What followed was a turbulent period of succession wars. Abaqa’s brother first took the throne but was overthrown by Abaqa’s son Arghun. Another of Abaqa brothers, Qonguram, plotted to overthrow Arghun but failed.
King Demetre’s son was married to the daughter of Mongol Chancellor Buqa, who was one of the conspirators against Arghun. Thus, the armies of the Mongols were poised to fulfill St. Basil’s prophecy. Seeing this truth, King Demetre repented and acquiesced to appear before the court of Arghun Khan in order to sacrifice himself for the safety of his Kingdom. He was imprisoned and executed and the anger of the Khan was sated.
At his death, those present witnessed the sun grow dark and the city enshrouded in gloom and shadow. His body was guarded by the Georgians present and then secreted away with help of fishermen back to Georgia. Today he is revered as a martyr saint with the title “the Devoted” or “Self-Sacrificer.”
Prophecy is a trope in fantasy and sci-fi storytelling because it is great tool for crafting interesting and exciting tales, as can be seen above with the story of King Demetre. In RPGs, however, prophecy is a tricky and even dangerous thing to play with. An author has complete control over everything that happens in the worlds she creates. A GM, however, has ceded that complete control to the players. Thus, if a prophecy is leveled at PCs, it can be abusively used to wrest that control back from the players begging the question: why play an RPG when the story can more properly be told as a short story or a novel?
If prophecy is to be used in an RPG setting, it really should to be part of what I call background noise. In other words, in context of St. Basil and St. Demetre the Devoted, the PCs would hear the rumor that the King had a prophecy leveled against him. The PCs can get involved if they want, or simply ignore it. Note that a good prophecy is one that has an “If…then” statement so that should players want to mess with it, they can be part of the force that can place pressure on whatever variable they wish.
At some point in the campaign (or even prior to the campaign) the prophecy is fulfilled and the PCs then have to deal with the consequences. To continue the example of Sts. Basil and Demetre, the PCs could be called upon to be those who secret the body of the King out of enemy hands.
In other words, prophecy in an RPG can still be a great tool; however, it needs to be a source of adventure background that players can interact with rather than something that is leveled at PCs that then players need to deal with.