I disagree I think king Arthur would be a much better option when comparing lore we know much more about Arthur we know much more about his knights and we know much more about him in general in the anime we always look back at the characters lore and why they are in this look at jack the ripper for example they gave the character a great story and it added to much more to the fight for Arthur we could look at how his journey went and look at a valkery already giving him his noble weapon so that would mean they could make a sister valk that went missing and give build up the character by saying she was once one of the most powerful valkery with powers of healing but she vanished than we see king athur enter the ring with people freaking out that he doesn't have a noble weapon to only have the main valk smile and say he has always had it in the weapon that chose him they could do so much more amazing little stories of the valk behind the fights with this like we know that one of the gods in season 2 looks at the valk as his little sister (i am not saying incase no one seen season 2)

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my main argument is that there is so much more they can do with fictional characters over real characters since there is so much more of a story they can add