Fate/Apocrypha

From the introduction: Welcome to the Nasuverse, in particular a timeline where during the 3rd Grail War the Einzbern Family decided not to try summoning a God of Evil and instead settled for gaming the system to get a Ruler Servant, one capable of using Command Seals on other Servants. Showing that this timeline isn’t too different from the others, they still managed to lose with this enormous advantage. On the plus side, the Greater Grail didn’t get corrupted. On the negative side….it got stolen by Nazis. Then stolen from them and has been hidden by a coalition of minor Magus families for several decades, while subspecies Holy Grail Wars were fought across the world – predictably, none of those ended well, with the possible exception of a certain Waver Velvet gaining the title of Lord El-Melloi, though now he has to deal with Flat. Now, finally, a genuine 4th Grail War dawns, but this isn’t the one you might recall from the tale of Fate/Zero.