In a parallel world to Fate/stay night, the Greater Grail vanishes after the Third Holy Grail War, only to resurface years later in the hands of the rebellious Yggdmillennia group. As tensions rise between them and the Mage's Association, a brutal clash ensues when fifty magi are massacred by Lancer of Black, leaving only one survivor to trigger the Greater Grail's reserve system. This event triggers the summoning of fourteen Servants, sparking the Great Holy Grail War in Trifas. Divided into the Black Faction led by Yggdramillennia and the Red Faction representing the Mage's Association, with a lone member from the Church, the war unfolds with the Grail appointing Ruler to oversee the battle as a neutral arbiter.