The Green Knight
Bercilak de Hautdesert, Bercilak of the High Desert
Sir Bertilak was the Green Knight of Sir Gawain and the Green Knight. He inhabited Castle Hutton. It is uncertain whether Bertilak himself was magical; personally I think of him as an ordinary mortal who cooperated with Morgan, and that the transformation and all other magic involved was her work.
Here is the way Gardner translates lines from the poem describing Bertilak in his human appearance:
An immense man, indeed, mature in years;
A beard broad and bright, and beaver-hued;
His stance was proud and staunch, on stalwart shanks;
His face flashed like fire; his speech was free;
Surely a man well-suited ...
To lead as lord in a land of gallant men.
In the later poem, The Grene Knight, he is called Bredbeddle. Malory’s Green Knight, Pertylope (Pertolepe), may be a derivation. L. H. Loomis notes that a similar character in Irish romance is called a bachlach (“churl”), which she suggests as the origin of Bercilak’s name (Loomis, Romance, 531-2).
Sir Gawain and the Green Knight | c. 1400