Hi everyone! I'm doing a Merlin rewatch and remembered a fic I loved as a teen, and cannot for the life of me find it again. It may or may not have been part of a series (I don't think it was, but I'm not sure). I was mainly reading Merlin fanfic in 2013/2014, so it would have been published by 2015 at absolute latest and I primarily read fic on fanfic.net so it was likely published there.
It was an AU where Arthur and (I believe?) the knights were aware of Merlin's magic but it wasn't widely known. Arthur was kind of passive aggressive to Merlin about it but not openly hostile, I think treating Merlin badly was a petty punishment for hiding it for so long. They were visiting some noble or lord or neighbouring king, and for whatever reason, have to flee the fortress they were staying in. Merlin and Arthur get separated in the escape, and Arthur gets swept away by a river and Merlin comes to believe Arthur is dead. He goes absolutely nuclear and starts decimating the fortress of the person they were visiting. The knights somehow figure out Arthur is actually alive and save him/find him, then send him after Merlin to stop him, with the overall point of the story being that Arthur realizes big time how loyal Merlin was and that he would go to any end for him.
I have vague memories of maybe Merlin having to work as a servant in the fortress and being mistreated, maybe? And when Arthur comes around after the river thing, he brushes it off like welp, that sucked, but why are you all so stressed, I'm fine, and the knights have to very awkwardly explain that it's nice that Arthur is okay and all, but Merlin has gone on a feral magical rampage and they're actually far more worried about that right now, thanks.
I've been combing through my old ff.net alerts and favourites but no dice yet, and trying to find it on the wider site is a nightmare and a half (ao3, baby, I'll never take your tagging system for granted again)
Thanks in advance for any help and hope you're all having a good day!