[When the ghost doesn't leave as he's told, and instead looks at them curiously, flapping its wings, Merlin yells at him again, just. very angry at this, at a dragon's image being used to mess with his head.
Then he's speaking more normally, the language changing as well, as he holds up a hand and casts a spell to get rid of the fog. When it clears up, the ghost disappears with it]