The Tavern Brawl was an incident that occured in Mary's tavern. It is where Arthur Pendragon and Merlin met Gwaine and had their first encounter with Dagr. It started off when the thug, Dagr, walking into the tavern and 'claming' his money from Mary. Apparently, Mary didn't provide Dagr with enough money so Dagr threatened her. But Arthur interveined, before Merlin only pushed the problem.
Then Dagr sent his other thugs into the tavern to battle Arthur and Merlin. Then Gwaine stepped in and said that they have gotten themselves into a lot of trouble, Gwaine started the brawl by throwing a puch to one of the thugs. The brawl was violent, but Arthur, Merlin and Gwaine could handle it. Even Mary stepped in and joined in with the fight. At the end, the trio defeated the thugs and Dagr was thrown in the stocks, but Gwaine was wounded (Gwaine).