User blog comment:Hitsuji Mamoru/FGO-style Servant Creation Room/@comment-28209103-20170204190246/@comment-28209103-20170205111214

Well my true reason as to why I put her as rider is the "lot of sun deity in rider category" part, but accidentally Tamamo is a caster so I add that reasoning on top..

If you think AuO or Ozy is haughty you're in for a suprise, originally true deity like Artemis or Amaterasu doesn't even saw human as something worth noticing, in Amaterasu cases she decided to pay attention on whim but originally she's the type that won't even look at AuO when they passed each other,, when she's in bad mood something the like of master or other servant won't be registered in her eyes and if she ever raged something like Ars Amandel Solomonis will looks like birthday candle.

her inital conception is "Extreme Tamamo" in the first place Tamamo are like the joke-chara of nasuverse, even as mere fragment she claimed that something like Solomon (Goetia) is a weakling if she were at 9 tails state not to mention she broke the 4th wall from time to time like saying "Experience point" or "Not being the main event heroine even if it's japanese themed event" or "Let's do Quest? Tamamo wanna rampage soon"  and so I took that and take it to the extreme.. the result is Amaterasu.