Preservers of Order (Zhongli Reader x FGO x DxD)

Chaldea was an organisation that summoned heroes from an alternative universe into their universe to act as the guardians of this world.

Unknown to the supernatural world, Chaldea is on the search for the Greater Grail in order to destroy it before it can fall into the wrong hands.

They send three artificial beings that house the spirits of three heroic spirits to find and destroy the grail but what happens when they find out that there's actually more than one grail