In this au, Merlin's frequent use of magic is causing a gradual transformation where he slowly develops dragon like traits (long hair, long teeth, etc..)
While he can manage the physical changes with haircuts and filing his teeth, the psychological impact is far more profound. He's becoming increasingly possessive and restless, exhibiting traits of a dragon guarding its hoard.
"Gaius, I don't understand why I feel so ill," Merlin says, his voice strained.
"Merlin, as a Dragonlord, it's possible you're experiencing hoard sickness," Gaius explains. "Dragons possess hoards of treasure and are fiercely protective of them. When deprived of their hoard, they suffer a debilitating fever until they reclaim it."
"A hoard? What could that be?" Merlin asks, bewildered.
"Think, Merlin. Has anything recently captured your attention or become particularly precious to you?" Gaius inquires.
Merlin struggles to recall, his mind clouded by a growing sense of unease.
As the months pass, Merlin's condition worsens. He struggles to fulfill his duties, his energy waning, and his personality shifting. He becomes short-tempered and withdrawn. The knights, Arthur, Morgana, and Gwen notice his decline, attributing it to a lingering illness. Arthur lessens his chores, and everyone gives him space, unintentionally isolating him further.
One night, the concerned group gathers secretly in Gaius's chambers, defying his orders to leave Merlin undisturbed.
"I can't believe we're doing this," Arthur mutters.
"Arthur," Morgana reassures him. "We're here to see Merlin. Besides, if Gaius catches us, we'll say we had urgent concerns."
"Still, this feels..." Arthur trails off.
"Relax, Princess," Gwaine interjects. "Everything will be fine. Don't pretend you don't miss him."
Suddenly, they hear voices and quickly hide. Merlin emerges, followed by a frustrated Gaius.
"I told you, I'm fine!" Merlin insists, his voice hoarse.
"No, you're not!" Gaius retorts.
"I said I'm fine!" Merlin's eyes flash gold, and a nearby vase shatters.
"It's alright, Merlin," Gaius soothes. "Here, try this new potion."
Merlin drinks the potion, then immediately vomits. "Ugh... I'm so sorry, Gaius. I don't know what's happening to me. It feels like I'm losing my mind."
"It's probably nothing," Gaius says, though his expression is troubled. "You just need rest and medicine."
The group witnesses this unsettling scene, their concern deepening. They realize Merlin's "illness" is far more complex than they ever imagined.