In 1264 Federico of Front was elected bishop of Ivrea, of the earls of  S.Martino. He continued the policy of enlarging the feudal system begun by his predecessors, attempting to extend the privileges and the lands of the Church in Ivrea. The same approach was taken by William the VII of Monferrato, on behalf of his family: By doing so a clash with Federico of Front was inevitabile.

The Marquis of Monferrato had sworn allegiance to Giovanni of Barone, former bishop of Ivrea, but the oath didn’t prevent him from taking over the city on the 12th June 1266. He manages to do it by a fraudolent and artful devotion, availing himself of the supporters he has in Ivrea. The submission was confirmed in Chivasso on the following 27th November, when the ambassadors from Ivrea were forced by threats to give William VII half of the incomes of the city. William used this dedication to build the Castellazzo which was for the most part destroyed in 1194 during the revolt against Ranieri di Biandrate.

The occupation of Ivrea by William of Monferrato found opposition from Federico of Front, who put the clergy and Arduino’s family against the former. There followed long and bloody fights between the supporters of the Marquis and those of the bishop. The latter succeeded in having William the VII excommunicated by Pope Clement IV; after the defection of his supporters, threatened themselves by excommunication, forced him to surrender to the bishop. Federico of Front succeeded in obtaining some years of ceasefire thanks to the protection of Charles d’Anjiou, king of Sicily; nevertheless, after the fall of the Anjiou power, on the 17th July 1278 William VII took over Ivrea and controlled the majority of Piedmont.

William VII died tragically in February 1292 following the revolt of Alessandria. He was kept in a cage hung from a tower and left to die. His cruel way of governing is recalled by Dante in the V Canto of Purgatory, who remembers him as he “who made Monferrato and the Canavese cry”. The successor of William VII was his son, John the first, who bore the name of Lord of Ivrea, but he had to share his power with Philip of Acaia. John I conquered Casale as well in 1303; he died at only 28 years old in 1305. After his death the Castellazzo, the hated symbol of feudal power, was destroyed a second time and for good.