Here are some excerpts from an introduction to the romance of "Sir Eglamour of Artois". Child has suggested that his number 18, "Sir Lionel", may be based on this romance.
"Sir Eglamour of Artois tells a familiar story of lovers separated by a disapproving father, their vicissitudes and eventual marriage in a triumph of faithful love. Despite its French locale, the poem seems to be of English origin; it has no known French analogues or antecedents. The romance was probably produced around 1350 somewhere in the northeast Midlands, perhaps in Yorkshire. To judge from the number of surviving manuscripts (six) and prints (four), it was widely known and well liked. The story's appeal is further attested by references to Eglamour in writings from the Middle Ages and Renaissance and the existence of other romances which show its influence: Emaré, Torrent of Portengale, and The Squire of Low Degree. The narrative was dramatized, for a London chronicle records that a play of Eglamour and Degrebelle was performed at St. Albans in 1444. The story circulated in ballads and one episode found in the romance may still live in Kentucky ballad tradition as "Bangum and the Boar...."
The story is given further moral and structural cohesion since the tests Egalmour undergoes form a graduated series developed in a parallel manner. Each combat is more difficult and lasts longer than the preceding one, and in each his opponents are more deserving of destruction. Eglamour easily slays the hart in the giant Arrok's dolorous forest and dispatches him after a day of battle. The boar is further away, in Sidon, and as Eglamour approaches, he finds the dismembered bodies of the beast's earlier opponents. The boar kills the knight's horse and requires three days to subdue, but his eradication is a great boon to the country which he had ravaged. In a further combat, undertaken of his own chivalrous volition, Eglamour defeats the boar's giant owner who has been demanding the king's daughter, Organata. After these trials, the knight requires a month's recuperation. The dragon of Rome is Eglamour's most formidable opponent - the most unnatural and destructive of all. The serpent has ravaged a whole city, the very center of Christendom. In this battle, not only is Eglamour's horse slain, but he himself is wounded, which Edmund Reiss suggests is punishment for his sin. The wound requires a year of healing in the care of the Emperor's daughter."
You can find more here: Sir Eglamour of Artois