The young, handsome Lord of Blackhaven, one of the castles of the Dornish Marches. Red of hair, he is betrothed to Lady Alia Dayne and has her nephew as his squire.
It’s unclear that Edric Dayne will appear on the show. Besides this, Dormer seems to match the character reasonably well, other than being rather older. It should be noted that the role was played by a featured extra in the first season, but was recast for the third season.
Lord Beric came to King’s Landing to ride in the Hand’s tourney, where he performed reasonably well. Due to his rank, more than anything, he was dispatched by Lord Eddard to lead a force to apprehend and bring to justice Ser Gregor Clegane. This force was ambushed, but Lord Beric and a few other survivors escaped to continue to fight against the Lannister forces.