Fate/Apocrypha: Aether Song

A dark route based off the Anime/Manga/and Light novel series Fate/Apocrypha.

Moments after the conclusion of Saber of Black, and Saber of Red's battle odd events began to occur. The hanging gardens of Babylon collapse with grail mud coming off of it, A monster runs rampant and defeats Ruler, and Most of the servants from both sides have gone missing.

Just what is going on, and can Sieg solve the mystery before the impending doom ends the world?