Crossover: King Arthur's Gender Is a Mystery

Life is always full of surprises, the male King Arthur said with a sigh as he looked at the female King Arthur before him. The female King Arthur's eyes were sparkling. "Are you here to take my place and lead Britain?!" The Old Saber looked bewildered. "What? I just got lost." Wait, is this the Sword Mound? Isn't this where I died in battle? Could I have come back again? Hold on, I remember dying. Wasn't I on my way to Avalon?! Why am I here?! The two King Arthurs stared at each other in confusion. The scenery around them had completely changed. They had transmigrated! That's right. The male King Arthur's chaotic spatial and temporal lines had caused both King Arthurs to transmigrate together! Just as Alaya reached out an olive branch, it discovered that the two King Arthurs had vanished! This is bad, this is bad, this is bad!! Gaia will definitely come after it! The legendary King Arthur, a figure of great importance to the world, hadn't returned to the Throne of Heroes! Gaia will definitely pound it into a little pancake! The protagonist is the Old Saber, and Saber is his permanent accessory. This story is full of fanon and all sorts of bugs. A crossover of crossovers, with Sword Art Online, Vampire, Harry Potter, Katekyo Hitman Reborn, Fate, The Avengers, and plenty more. I'll write whatever comes to mind!