in fief from Venice as confirmed in a charter issued by Doge Pietro Ziani (). Michael granted the Venetians extensive trading privileges and tax exemptions, just as they had enjoyed under the chrysobulls of Emperor Manuel I Komnenos (), promised to expedite the grain exports to Venice, and to assist in any shipwreck of a Venetian vessel off the Epirote coast. In addition, as a sign of his vassalage he would pay to the Venetian duke of Dyrrhachium an annual tribute of 42 litrai of gold hyperpyra in two instalments, and send annually a rich brocade for the altar of St. Mark's Basilica and one for the Doge. Ransoming of Alexios III At about the same time, Michael's rule received a boost in legitimacy through his ransoming of emperor Alexios III. After his deposition by the Crusaders in July 1203, Alexios with his wife Euphrosyne Doukaina Kamatera had been roaming Greece seeking protection. A marriage alliance with Leo Sgouros failed due to the latter's hasty retreat before the advance of Boniface of Montferrat. Left stranded in Thessaly, Alexios was captured by Boniface. The former emperor was initially held in comfortable captivity, but at some point he fell foul of Boniface; sources differ on whether he tried to flee to Michael's domains and was captured by Boniface's knights en route or whether Boniface simply came to distrust him as a potential rival focal point for the loyalties of the Greek population. He and his wife were then imprisoned, either in Thessalonica or, according to other sources, in Montferrat. Learning of their fate, Michael offered to ransom the former imperial couple and eventually secured their release, welcoming them at Salagora, the port of Arta, where they arrived by ship. Michael treated the couple with every courtesy, but Alexios did not remain long in Arta. The deposed emperor was eager to regain his throne by taking over the Empire of Nicaea with the aid of the Seljuk Sultan Kaykhusraw I. Leaving his wife behind, and accompanied by Michael's half-brother Constantine Komnenos Doukas, Alexios took sail for Asia Minor. His attempt ended in complete failure in the Battle of Antioch on the Maeander in 1211, where Theodore I Laskaris killed Kaykhusraw and took Alexios prisoner. The hagiography of St. Theodora of Arta claims that on his departure, Alexios granted Michael and his descendants hereditary possession of his domain, while the 14th-century Aragonese version of