Merlin had initially doubted the dragon's words. How could someone like Merlin be destined to protect the child of a man who would see Merlin's head roll across the castle courtyard?
He had always been sure that the dragon has gotten it wrong, that he couldn't be this all powerful Emrys that has been written about. His path couldn't lie with Arthur's. Not Arthur who cuffed him around the head every chance he got, and took every opportunity to point out Merlin's obvious lack of skill in everything.
He'd remained unsure through everything. Saving Arthur from the vengeful witch-mother had been coincidence. But then he'd taken the poisoned goblet from Uther's hand and the world had gone black. Yes, Arthur had ridden out to find the cure, but the quest for the Morteus was just Arthur's sense of honor taking control. Sophia and Aulfric were a danger to everyone and had to be stopped. Merlin told himself that only saved Arthur because that is just the kind of person Merlin is. It has nothing to do with coins, or halves, or anything else the dragon has said. Then he woke in a bed too warm to be his, with a blond head tucked securely under his chin, and Merlin had let himself think that maybe uncertainty was all a part of the plan.
Except now Arthur knows about him. He's seen the flash of amber in Merlin's eyes, heard the harsh foreign tone of the incantation, and seen the beast before them vanish into the air. Merlin hears the sharp intake of breath behind him, and he knows now that the dragon has always been wrong. Sorcerer.
He steels himself as he turns around. I never believed the lie anyway, and I'll be no different than I was before. But when Arthur turns away from him, his blue eyes cold as ice and unfeeling, the foundation of the Earth suddenly slips away. There is no fury, no rage, and Merlin is a man drowning in nothingness, grappling for purchase at anything he can find, and eventually clinging to one word because true or not, it is all he has left.