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.
I really like 'Avalon's Arthur in Fate Fanfic'. In this story, Arthur has a deeper connection with Avalon, his mythical resting place. It gives a fresh perspective on his powers and his relationships with other Fate characters. Then there's 'Arthur's Allies in Fate'. This fanfic focuses on Arthur forming new alliances and how those relationships shape his journey in the Fate world. 'The Pendragon Legacy in Fate' is also good. It explores how Arthur's legacy affects the present - day Fate universe and the characters within it.
One popular character paired with Arthur in Fate fanfic is Saber. Since she is an incarnation of Arthur in some versions of the Fate series, they often have complex interactions. Another is Merlin. He is Arthur's mentor and advisor in the original legend, so in fanfics, they are often shown having deep conversations and Merlin guiding Arthur through different situations. Also, Artoria is commonly paired with Arthur as they are both related to the Arthurian legend and can have interesting dynamics in the Fate fanfic world.
Maybe Arthur Pendragon gets transported to the Fate world and his presence disrupts the normal balance of power. The mages in the Fate universe might see him as a threat or an opportunity. He could end up being a wild card in the Grail War, not bound by the normal rules of Servant summoning. His noble phantasm, Excalibur, could be a game - changer in battles against other powerful Servants.
She influences his fate greatly by giving him Excalibur. This sword is central to his identity as a king. Without it, he might not have had the same level of success or the aura of a rightful ruler.
I recommend you to read "From Genius to Invincible," which is a fated Doujin novel with King Arthur as the main character. The story was adapted from Battle Through the Heavens, so I'm sure you won't be unfamiliar with it. I hope you like this fairy's recommendation. Muah ~😗
Yes, the male protagonist of the novel "The Martial Arts I Cultivated Mutated", Ye Xuan, had transmigrated to a world where reiki was recovering. When he obtained a martial arts manual, he activated the martial arts mutation system. He was able to use Iron Skin Technique, Nine Yang Divine Technique, and various other variant martial arts. The plot of the book was mainly about him adventuring in various worlds through the martial arts system, including the world of Fate and the world of King Arthur, Altolia. Therefore, in this novel, there was a male protagonist who could use martial arts to travel to the world of King Arthur in Fate. I hope you like this fairy's recommendation. Muah ~😗
According to the information provided, I can recommend a novel related to FATE-Immortal Death Knight failed to achieve the ending of the heroic spirit. This novel is a light novel-derivative doujinshi novel, describing the unusual ending of the heroic spirit Saber. However, there was no clear information about the identity of the female protagonist Saber in her previous life, so the question could not be answered.
Arthur could be a professional writer as well. He might be working on his next best - selling novel. He has a routine of sitting in his study, surrounded by books and a laptop, and he spends hours crafting this story, thinking about the plot, the characters, and the overall theme.