Mercia is a kingdom in Albion that is ruled by Lord Bayard.
The kingdom was at war with
Camelot for many years. Finally, Bayard and Uther Pendragon agreed to a peace treaty, which was almost upset when Nimueh framed Bayard for the attempted assassination of Arthur Pendragon. Uther's court physician Gaius uncovered the truth before Mercia's troops attacked Camelot for Bayard's imprisonment, and the two kingdom's presumably reached a peaceful settlement after that ( ).
The Poisoned Chalice
Morgana and Gwen were kidnapped and Kendrick's men intended to hold them hostage, Arthur believed Mercia was behind it because of the swordcraft ( ).
Lancelot and Guinevere
Bayard is later called a "friend of Camelot" by Uther ( ).
Beauty and the Beast: Part Two
Arthur went on a quest for the Fisher King's trident, Mercia appeared on the map so it's presumed that he went past the kingdom ( ).
The Eye of the Phoenix
Arthur became King of Camelot, Agravaine questioned that Mercia is a threat and is not to be trusted, despite the peace treaty ( ).
His Father's Son In The Legend Edit
In actual history, the kingdom of Mercia was Anglo-Saxon, established after the supposed death of
. It covered much of south Derbyshire, Leicestershire, Nottinghamshire, Staffordshire and Northern Warwickshire. For some time it was the most powerful Kingdom in Britain.