Fortress of Millennia

The fortress where the “Black” Masters and Servants are gathered. It is a huge fortress that is big enough to take up half the area of Trifas. It is even bigger and more complex than most famous European castles, and it has been made unbelievably secure thanks to the combination of various Mystic Codes and defensive spells that Yggdmillennia has stored there over the past sixty years. Homunculi continue keeping guard day and night, and golems that move to intercept the moment they sense movement are hidden in some of the pillars, floors and ceilings.
The clan's leader, who has barely aged at all, is a good example of what happens when you manically prepare beforehand. However, half of all those scrupulous preparations were blown away with a single punch from a certain mad warrior…

Fate/Apocrypha material: Fate/Apocrypha Encylopedia