As one of the leading nobles of the Latin kingdom of Salonika, Guido continued to be associated with its fortunes. In 1221 we find him acting as bailie for the Regent Margaret during the minority of the young King Demetrius, in whose name he ratified a convention with the clergy respecting the property of the Church[337]. His territory became the refuge of the Catholic Archbishop of Larissa, upon whom the bishopric of Thermopylæ was temporarily conferred by Honorius III, when the Greeks of Epeiros drove him from his see. And when the ephemeral kingdom had fallen before them, the same Pope, in 1224, ordered Geoffroy II de Villehardouin of Achaia, Othon de la Roche of Athens, and the three Lombard barons of Eubœa to aid in defending the castle of Boudonitza, and rejoiced that 1300 _hyperperi_ had been subscribed by the prelates and clergy for its defence, so that it could be held by “G. lord of the aforesaid castle,” till the arrival of the Marquess William of Montferrat[338]. Guido was still living on May 2, 1237, when he made his will. Soon after that date he probably died; Hopf[339] states in his genealogy, without citing any authority, that he was killed by the Greeks. He had survived most of his fellow-Crusaders; and, in consequence of the Greek reconquest of Thessaly, his Marquisate was now, with the doubtful exception of Larissa, the northernmost of the Frankish fiefs, the veritable “March” of Latin Hellas. Guido had married a Burgundian lady named Sibylle, possibly a daughter of the house of Cicon, lately established in Greece, and therefore a cousin of Guy de la Roche of Athens. By her he had two daughters and a son, Ubertino, who succeeded him as second Marquess. Despite the feudal tie which should have bound him to the Prince of Achaia, and which he boldly repudiated, Ubertino assisted his cousin, the “Great Lord” of Athens, in the fratricidal war between those prominent Frankish rulers, which culminated in the defeat of the Athenians at the battle of Karydi in 1258, where the Marquess was present, and whence he accompanied Guy de la Roche in his retreat to Thebes. In the following year, however, he obeyed the summons of the Prince of Achaia to take part in the fatal campaign in aid of the Despot Michael II of Epeiros against the Greek Emperor of Nice, which ended on the plain of Pelagonia; and in 1263, when the Prince, after his return from his Greek prison, made war against the Greeks of the newly established Byzantine province in the Morea, the Marquess of Boudonitza was once more summoned to his aid[340]. The revival of Greek power in Eubœa at this period, and the frequent acts of piracy in the Atalante channel were of considerable detriment to the people of Boudonitza, whose food supplies were at times intercepted by the corsairs[341]. But the Marquess Ubertino profited by the will of his sister Mabilia, who had married Azzo VII d’Este of Ferrara, and bequeathed to her brother in 1264 her property near Parma[342].