This can happen in any of the Fate Series. If in Zero and Stay Night, then it will be the reincarnation of Nobunaga acting as a Master.
If in Apocrypha he can be a student going to Trifas for a trip and become a Master or the Servant Fooler, summoned by Jeanne D'Arc.
Should it be in Grand Order then Nobunaga can be a Master and the Cause of the First Singularity in France by saving Jeanne while claiming himself to be a demon or something. He could also save Avenger Jeanne Alter. The Servants he has can be those that are 'Evil' in a sense and those that have been betrayed by humanity in a sense. Along with most if not all the Japanese Servants. He can follow a Good, Neutral, or 'Evil' route.