User blog comment:Hitsuji Mamoru/Servant Creation Room 2 : Guess of the Who/@comment-31726296-20170716053325

Well I hope she is fictional, ha ha, or else calling her Caster of Doujins would be stupid of me.

You could check out the skills first. because all skills other than Amnesia are official skill from the game. which would result in you and other finding out what ??? Magecraft and ??? are and identifying the servants true nature.

Also I should mention that their are two people speaking in her Introduction Line (True Name Concealed) ( After First Ascension). the heroic Spirt is call caster and the Anonymous Speaker s ???. sorry for that, for some reason that I didn't realize that it might confusing people to have two different ??? mentioned in the sheet. Well you are in luck. We  agree on A compromise. she is allowing me to say her name is 4 letter long and starts with a R.

Also maybe the Anonymous Speaker, who's name starts with an R, could be talking about that formidable magical girl. However, do to the True Name System in FGO she could not said the words properly?

in addition to that she is similar to Goetia in fate GO, but instead of hijacking the body after the soul left it. instead caster required hers after someone gave up their body to allow caster to live on after an atrocious battle.

I hope this help in the exposition of the character.