Talk:Moon Cancer/@comment-39954983-20190818180111/@comment-35539022-20190913004038

I always just accepted the 7 main class affinities as losely based on F/SN and reason and overall just a mechanic invented for gameplay purposes (as FGO would've been a far more complicated game if affinity wasn't a thing and they had to make other mechanics. Plus it's canon that class advantage has no bearing outside of FGO, all main classes are equals and have no special bonuses.

As for Ruler vs Avenger vs Moon Cancer, I came to understand it like this (at least it's what makes sense to me).

Rulers are adjudicators of the Holy Grail wars and serve as direct agents of the grail to protect it's interests and ensure the rules be fulfilled. Rulers thus are "created by the grail", "creator and created". Avengers are the dark side of the cup, "it's contents" so to speak. That means they are made from the same magic and corruption and curses that create the holy grail, it's "contents". One could say, "they are the grail itself", no class draws it's power from the grail more directly than Avengers. Moon Cancer is a class specific to BB, she actively opposes the grail and is a means to it's downfall, she rebels against it. "The cancer of Moon Cell."

If A=B and B=C, then A=C. If BB is the Cancer of the holy grail, and Avengers in a sense ARE the grail, then BB is the Cancer of Avengers. If the grail is higher than Rulers, and Avengers are the grail, then Avengers are higher than Rulers or it's a case of the creator superceding the created. Finally, if Rulers are dispatched to protect the grail and it's will, then BB is automatically their enemy, hence Rulers will proceed to take out any and all Moon Cancer.

As for the relationship between Alter Egos and Foreigners I have no idea as conceptually they're a little difficult to understand.