User blog comment:Vremyanova/Speculated Future Servant, Short Introduction, and Their Possible Class/@comment-27247829-20160129154259/@comment-27654842-20160129160121

Literally Nasuverse knock-off are everywhere lmao.

I only put the possible class based off their occupation and profile off Wikipedia and other history sites. The only known qualification for Ruler is that: they have to be a devout religious person, and they have no wish to make to the Holy Grail. (at least, that's how Jeanne describes it in Fate/Apocrypha. Though Amakusa Shirou Tokusada, who cooks up some weird shit, also managed to become Ruler)