Book V, Canto X
Spenser spends the first part musing on the implications of Mercilla as Elizabeth, the relationship of mercy and justice, and the death of Duessa as an act of mercy.
Soon a pair of young men arrive at the court. They are the sons of the widow Belge, and are asking for help for their land. This entire canto is another political allegory, this time for the Spanish Catholic dominance of the Low Countries. Their tyrant is Geryoneo the son of Geryon, whom Hercules had killed. Geryoneo fled to Belge’s land, slowly gained control, and set up an idolatrous reign that Spenser identifies with the Spanish Inquisition.
Arthur volunteers to go with the youths to save Belge. He finds her hiding in the marshes, most of her cities sacked and razed. Arthur goes with Belge to her former castle, now given over to Spenser’s vision of Catholic idolatry. Arthur fights the seneschal of the castle, then three other knights, and slays them all. Thus they win the castle.