Fate/Grand Order: Moonlight/Lostroom

The Lost Room. A place where you can see what was lost, or maybe what will be lost to you in time. Existing in the innermost part of Chaldea, it is the boundary line between dream and reality where the light of the moon shines through. Produced by the Chaldea Summoning System, the room holds a small number of worthwhile benefits to enjoy.

(Source: Crunchyroll)