A/N: I started watching Merlin this summer right after a huge Highlander binge. So, of course, what do I immediately think of? WARNING: Obvious plotholes that for the sake of this crossover piece are happily ignored.
Methos feels bad for forging the letter, but he has to get out of Ealdor now, and he's been forging documents since they were chopping nicks into stones. Besides, he knows Hunith well enough to pretend to be her son. So he fabricates the letter, chooses a new name, washes the dye out of his hair, and nicks some belongings from the local boys. The stodgy aging carpenter is now gone; in its place is a fresh-faced youth, awkward and gangly and earnest. Years in the future, this persona will be called Adam Pierson. But in old Britain, he chooses a one better suited to the times. Merlin.
Methos doesn't expect Merlin to become a sorcerer. He knows that in this land, powers such as those are usually met with a head chopper's block – one of the few punishments he truly and terribly fears. Merlin is meant to be a bumbling physician's apprentice (because he hasn't been a doctor for a couple centuries, and Methos likes to keep those skills sharp – and the bumbling part? Well, that's just fun) who knows nothing, but might one day throw a couple of ingredients together by accident and pass on some of those old Babylonian remedies he still remembers. It's a safe, non-risky, non-assuming identity.
However, Gaius almost falls to his death and Methos can't let his new life slip away that easily, so he summons that strange skill he's always had to move objects and gets called a sorcerer. Merlin the Sorcerer, Methos muses. An odd name. But apparently, a name weighted with destiny. The dragon living under the castle certainly thinks so.
(Methos's always loved baiting dragons.)