Conradin sent letters and manifestos to Italy and even to Rome, in which he announced that he was coming to claim the rights of his ancestors and called himself King of Sicily. The Pope consequently instituted a suit against him in Viterbo; he published this document and at the same time a bull, in which he forbade the electors of Germany ever to elect Conradin King of the Romans and threatened all his adherents with excommunication.

“I do not lay much stress,” wrote Clement IV. in October 1266, “on the envoys whom the Ghibellines have sent to their idol, the boy Conradin; I am too well acquainted with his position; it is so pitiable, that he can do nothing either for himself or his adherents.” But in the spring of 1267 the reports became more decided, the demeanour of the Ghibellines in Tuscany more threatening. On April 10 the Pope wrote to the Florentines. “A poisonous basilisk has arisen from the stock of the dragon, which already fills Tuscany with his pestilential breath; he sends forth to cities and nobles a brood of vipers, men of destruction, the accomplices of his schemes, traitors to us and to the vacant empire as to the illustrious King Charles; with his lying artifices he parades himself in glittering splendour and endeavours, now by entreaties, now by gold, to seduce men from the ways of truth.