The maiden loved by Pelleas in the Post-Vulgate Suite du Merlin. Malory calls her Ettard.
Pelleas awarded her the crown at a tournament in which he defeated sixy knights, but Arcade continually rebuked and scorned him. He followed her to the country of Arroy, where he kept vying for her love. Every day, she sent ten knights against him, and every day he defeated them all but let them capture him anyway so that he might a glance of Arcade on the way to her prison. Then, Arcade’s men would humiliate him and release him in the forest.
Gawain learned of Pelleas’s plight and offered to help him by visiting Arcade. Bringing Pelleas’s armor with him, he told Arcade that he had killed Pelleas. Whatever his plan had been, Gawain abandoned it when he saw Arcade’s beauty. He slept with her, betraying Pelleas. Pelleas found them together in an outdoor pavilion. After considering killing them, he finally decided to lay his sword across their throats and depart. When Arcade awoke, she realized that Pelleas had been there and that he was still alive.
Gawaine confessed his fib and persuaded Arcade to reconcile with Pelleas. The two married and had a son named Guivret the Younger.
Source
Post-Vulgate Suite du Merlin | 1230-1240
Le Morte Darthur | Sir Thomas Malory, 1469-1470