User blog comment:Valeth/Random Musings - Did Lore Segregation happened on FGO Gacha?/@comment-32751919-20181202034042

That was a great blog I has read so far.

Despite it never explain in lore-wise, but it sound very make sense and explain how and why they are summonable/unsummonable.

And maybe why Proto Cu*, Ozymandias, Paracelsus and Arash (I don't if Hassan of Serenity or even Brynhildr (who is limited) are count) are summonable because they main world version and alternative world version aren't different from each other, so they consider as "same person".


 * Proto Cu consider to be "younger version" of Stay Night's Cu

But face it, it's DW's fault to gain more money.