An AU I desperately want and will probably have to write myself:
In "The Beginning of the End," Merlin has a very healthy reaction of "whoa there friend" after Kilgharrah tells him to more or less murder a small child, and instead of having Mordred try to escape with Morgana, he's just like, "nah, I got this." The guards didn't actually see Mordred, anyway. They saw a child in a cloak running away, so Merlin ditches the cloak, finds Mordred some new clothes 'borrowed' from a squire or a page, and then he just...hides the kid. Castles are fuckin' huge. Merlin's gotten lost a hundred times on accident. Surely he can lose a child on purpose.
So begins the most hardcore game of Hide and Seek. Merlin straight-up steals food from the kitchen for Mordred, and both Gaius and Arthur probably think he's a little bonkers, considering he keeps running off where neither of them can find him, or staring off into space and occasionally laughing at nothing (bc he's mind-speaking with Mordred so the kid doesn't die of boredom). It takes a good three weeks before Uther finally gives up the search and says the boy must've escaped, and then there's a moment of "what now?" And Merlin (having used his turn on the braincell to come up with the plan to hide the kid) just kinda looks at Mordred and goes, "Hey, wanna learn magic shit with me?" To which Mordred immediately replies with his whole 11-year-old chest, "Feck yeah."
Gaius, predictably, loses his shit when he finds out, but Merlin is a stubborn little shit, so guess who wins that argument? Of course, Mordred isn't just content learning magic with Emrys, he wants to meet the Once and Future King, too. Which leads to Arthur being baffled AF because why does Merlin have a small child and where did he get it from? Merlin isn't old enough to be his father (even if they do look weirdly alike) and Merlin's never mentioned a brother, so...?
(He thinks about the Druid boy that the guards couldn't catch, a young, injured child on his own escaping from an entire city of guards and knights, and how strange his manservant had acted in those days, and how this child is appearing just when the search is called off.)
And from then it's just a series of various shenanigans building up to that ever delightful Found Family consisting of a warlock, a prince, and their illegal Druid child. Merlin teaches Mordred magic and physician stuff, and Arthur eventually gets around to teaching Mordred how to shoot a crossbow and use a dagger (which is immediately confiscated because "daggers are for good children who don't try and hamstring anyone who speaks badly of Merlin") and Morgana is like the fun vodka aunt, except she's more like, "Hey, wanna commit treason against Uther?" while Gwen in the background is just, "Morgana, no."
Arthur asks Merlin one (1) time about where Mordred came from, during his daily 10 seconds of braincell-time. Slips it into normal conversation: "Merlin, is Mordred the fugitive Druid boy?"
And Merlin "Nat 1 Deception" Ambrosius immediately and without hesitation says, "What's a Druid?" and walks away.
And Arthur is left standing there like đ "dick game good to have me dealing with this level of dumbfuckery."
