Saber from Fate/Stay Night would be an obvious choice. Since she is also related to the Arthurian legend, there could be a lot of interesting interactions between them. They could compare their experiences as king, or even fight side by side against a common enemy.
The plot is full of adventure and fantasy. It follows a group of knights on a quest to save the world. The appeal lies in its rich world-building and compelling characters.
One of the main adventures is the quest for the Holy Grail. Many knights set out on this perilous journey. For example, Sir Galahad was one of the purest knights who had a significant role in this quest. They faced numerous challenges like battles with fierce enemies and magical obstacles along the way.
One possible reason could be a misunderstanding. Maybe Merlin did something that Arthur misinterpreted as betrayal or dishonesty. For example, if Merlin was secretly helping an enemy for a greater good that Arthur wasn't aware of at the time.
One great Arthur Pendragon hurt fanfiction is 'The Wounded King' which delves into his emotional turmoil after a major battle. It shows his struggle to regain his strength both physically and mentally.
Well, in such a fanfiction, they could team up against a common enemy. Maybe an ancient dark force that has been awakened in both their times. Their combined knowledge of magic from different eras would be a great asset.
One great 'Arthur Pendragon Merlin fanfic' is 'The Once and Future King' -esque story where Merlin's magic is a key factor in Arthur uniting the kingdoms. It shows their deep bond and how Merlin uses his powers to protect Arthur in a very creative way.
A fanfiction that stands out is 'Arthur and Merlin: A Different Path'. This one takes a different turn from the original storyline. It imagines a world where Arthur discovers Merlin's magic much earlier. This changes the whole dynamic between them, and they face different challenges together. There is also 'The Adventures of Merlin and Arthur in the Enchanted Forest'. It's full of exciting quests and the development of their friendship.
Well, there were quite a few well - known knights among the 12. Lancelot was famous for his great combat skills and his complex relationship with Queen Guinevere. Gawain was known for his honor and was often involved in various quests. Percival was on a journey to find the Holy Grail. There were also knights like Bedivere, who was with King Arthur till the very end.