Well, as for who would have played the arthur role in the last campaign, the first falcon King would be a good guess. Very much a sword in the stone type tale, but with an extended timeline. The Good kingdom falls, and the last of the line is hidden with a trusted vassal lord, and raised as his son.
Time passes, and eventually one of the descendents of the hidden prince discovers his heritage (and here he thought he was just the son of a lowly
Baron for all of this time), including 13 magic swords hidden in great Rune Stones all across the land.
Whosoever pulleth out those swords from those stones is the right-wise ruler of the Kingdom...
But the evil woman of shadow wants her own son on the throne, and sonny-boy is not entirely without ambition. So, bad king and good king end up starting a civil war as the old empire
*cough* Rome *cough* loses control of the island of kings
*cough* Britain *cough*, and eventually of the entire known world
*cough* Rome, again *cough*.
But the good king is not without a patron. Just as the bad king (Mordred) has a mother of power, as the good King's true father dies, a being of power steps in to guide the potential King (Oberon).
Meanwhile, allies of both of the leaders gather armies, and clash in hundreds of battles across the kingdom. Good triumphs over evil, and (unlike the french versions of the Arthurian legend) a golden age!
Just goes to show you how unoriginal I can be, eh?

While the Arthurian themes are a little less obvious in this game that they were in the last, it is not entirely without them.