The showdown with Emrys occurred after Merlin had disguised himself as an old man so he could go to Morgana's Hovel without being recognised and kill the Fomorroh that was unintentionally forcing him to try to assassinate the King.
Shortly after he had cast an ageing spell on himself and tried to get back on his horse, he was cornered by the Knights of the Round Table, who wanted to arrest him and take him to Camelot. At first Merlin tried to talk his way out, but then he decided to induce the knights into attacking him by threatening King Arthur's life and by making Gwaine angry. When Emrys told him that he couldn't hear what he was saying because he had ale in his ears, Gwaine yelled and attacked him, but the "old" sorcerer held up a hand and stopped him dead in his tracks, knocking him out with a stunning spell. Percival tried next, but Old Merlin broke the blade of his sword in half and magically shoved him and Sir Leon into each other, throwing them on top of Elyan. Laughing, he used them as a set of stairs to climb onto his horse before riding away (A Servant of Two Masters).
|Series 1: Merlin vs. Arthur • Arthur vs. Valiant • Merlin vs. Edwin Muirden • Sir Owain vs. Tristan de Bois • Sir Pellinore vs. Tristan de Bois • Uther vs. Tristan de Bois • Arthur vs. Evan • Merlin vs. Tauren • Merlin vs. Kilgharrah • Merlin vs. Nimueh
Series 2: Merlin vs. Jonas • Arthur vs. Morgause • Arthur vs Uther • Olaf vs. Arthur • Arthur vs. Kilgharrah
Series 3: Merlin vs. Morgana • Merlin vs. the Goblin • Merlin vs. the Sidhe elder • Gilli vs. Nollar • Uther vs. Gilli • Morgause vs. Merlin & Gaius
Series 4: Showdown with Morgana • Uther vs. The Gleeman • Arthur vs. Derían • Emrys vs. the Knights of the Round Table • Emrys vs. Morgana • Arthur vs. Sir Lancelot • Arthur vs. Sir Elyan • Arthur vs. Helios • Guinevere vs. Morgana
Series 5: Arthur vs. Odin