Fate Dark Descent

During a routine exploration of a rogue Singularity everything goes wrong as Ritsuka falls prey to the schemes of a Foreigner Servant. Who uses a Holy Grail to transform the hapless Magus into one of the Outer God, Shub-Niggurath's, Dark young. Now cut off from Chaldea's systems and cast into a strange new world can the wayward Master make it back to her friends?