Fate/Apocrypha Season 1

Fourteen Heroic Spirits gather for an apocryphal Holy Grail War. In a city called Fuyuki, seven magi and their Heroic Spirits once clashed in a Holy Grail War. But amid the chaos of the Second World War, a magus made off with the Grail. Decades later, the Yggdmillennia clan holds the Grail high and secedes from the Mage's Association, declaring their independence. Angered by the move, the Association sends assassins after them, only to have them wiped out by a Yggdmillennia Servant. The choice is made to fight Servants with Servants, and the Holy Grail War system is expanded to two factions of seven Servants each. A Holy Grail War of unprecedented scale -- a Great Holy Grail War -- begins in Trifas, Romania.