That strike is delivered after the protagonist beheads a man disguised by Morgan
 le Fay on Christmas Eve.
The introduction to this work summarizes the historical lead-up to the foundation of Britain, starting
 with the sack of Troy. The protagonist of this work rides his horse Gringolet to a castle on Christmas Day,
 where he refuses a golden ring before receiving a silk girdle from a woman. He keeps this gift secret from
 the lord of the castle, Bercilak da Hautdesert, causing the protagonist to bleed heavily from an axe blow to
 his neck later in this work. That strike is delivered after the protagonist beheads a man disguised by Morgan
 le Fay on Christmas Eve. For 10 points, name this Middle English work of literature attributed to the Pearl
 Poet that focuses on a knight of King Arthur's court.
The introduction to this work summarizes the historical lead-up to the foundation of Britain, starting
 with the sack of Troy.
Sir {Gawain} and the {Green} Knight