In 1259, Geoffrey participated in the princely army that joined the Achaean–
Epirote–
Sicilian alliance opposing the
Greek Empire of Nicaea. The allied forces, riven by distrust between the Latins and the Epirote Greeks, were dealt a crushing defeat in the
Battle of Pelagonia. Prince William and most of his barons, including Geoffrey, were captured in the aftermath of the battle. The Frankish lords remained in captivity until 1261, when, following the recovery of
Constantinople by the Nicaean Greeks, the Emperor
Michael VIII Palaiologos offered to release them in exchange for an oath of fealty to him, and the cession of a number of fortresses in the southeastern Morea. After William agreed, Geoffrey was released in order to convey the emperor's proposals to the nobles of the Principality. A parliament was once again held in Nikli, in the presence of Geoffrey, Guy de la Roche, and the Principality's chancellor,
Leonard of Veroli. The captive lords were represented by their wives, whereby this assembly became known as the "Parliament of Ladies". The parliament agreed to the terms, Geoffrey handed over the castles to the Greeks, and returned to Constantinople along with a number of hostages, whereupon Prince William and his barons were released. The surrender of the fortresses began a long period of conflict between the Greeks of the reconstituted
Byzantine Empire and the forces of the Principality for control of the Morea. Prince William was absolved by the Pope of his oaths to Palaiologos, and warfare began almost as soon as he returned to the Principality. Despite this precarious situation, Geoffrey absented himself from the Morea, without William's permission, and spent the years 1263–1265 in Italy, ostensibly on a pilgrimage, but in reality living with the wife of one of his feudatories,
John of Katavas. His absence allowed the inhabitants of Skorta to rise up and aid the Byzantine troops in their offensive, which was halted by the same John of Katavas in the
Battle of Prinitsa. Geoffrey was again deprived of his barony for this act, but was pardoned and restored to it on his return. ==Final years and death==