The older cousin of Guinever was a young man with eyes like the dawn. 

Accolon was beloved by the people of his uncle and foster father's lands, especially once he took up the role of a knight errant and began traveling. Everywhere he went he excelled in tournaments and helped others, becoming a hero to their small kingdom. And soon the people began to speculate on who he would marry, the whispers growing louder once Guinevere was married to the newly crowned King Arthur. But Accolon would only smile when asked, shaking his head mutely. 

For the truth was he had a lover already.

A beautiful woman he knew only by the name of Morgana, who had utterly stolen his heart. The two had met by chance, Morgana having been gathering flowers at the lake Accolon had led his horse to to rest. From there they swiftly fell in love, even with Morgana's admission of being half faerie. 

Soon enough, however, Morgana began to push Accolon to joining King Arthur's court of knights. His Round Table, as it was called. And Accolon, seeking only to bring her happiness, followed through with her guidance. Proving himself to the young king and his knights, the queen's cousin soon settled in comfortably in the castle. But his views would soon sour. Seeing the cousin he had loved as a baby sister stuck in a marriage with a man who did  not love her, who would not love her, infuriated him though he kept it hidden carefully behind the golden smiles. And soon enough that anger and resentment fueled his personal and private desires for kingship, his wishes to rule.

Thus, he began to plot.

Bringing his concerns to Morgana, his lover helped him figure out the perfect plan- and to set it in motion.

During one of the rare days that King Arthur was able to slip away from both his knights and the castle itself to ride his horse, Accolon would from the shelter of the trees shoot Arthur with an arrow coated with a potion to induce sleep. Then, he and Morgana spirited Arthur away to a hidden castle where he would be kept imprisoned and stuck in a magical sleep. With that done, Morgana provided him with a ring that would alter his appearance and voice just enough to fully resemble Arthur. 

So with Excalibur in hand and Arthur imprisoned within a deep sleep, Accolon returned to Camelot. 

For the next several months his plan continued without a hitch. 

Accolon ruled, with all but a few people fully believing he was Arthur. 

Were it not for those who were not fooled, his plan would have succeeded. But those closest to Arthur went in search of the young king, and, upon finding him, brought him back to Camelot. 

Arthur challeneged Accolon to a duel, regardless of Accolon currently holding Excalibur and Arthur wielding only a simple steel blade. 

In the end, Accolon lost the duel as villains are destined to do, and thus did his tale end. But his lover? It turned out Morgana was Morgan le Fae, and through Accolon's machinations she had stolen the sheath to Excalibur, leaving Arthur vulnerable to injury and illness.