Fate/Apocrypha

The Holy Grail War is a battle royale between 14 master-servant pairs, with each side, Yggdmillennia and the Mage's Association, aiming to possess the powerful relic. The conflict began when the Association sent 50 elite magi to retrieve the Grail, only to have them killed by a mysterious servant. This led to Yggdmillennia declaring war on the Association, which resulted in the unusual format of the Holy Grail War, where the first side to lose all its combatants will forfeit the artifact. The war pits seven master-servant pairs from each side against each other in a fight for the Grail.