In 1281 Abaga was poisoned by his brother Achmed,[477] and Maria deemed it prudent, and doubtless welcome, after an absence of sixteen years, to return to Constantinople. She appears again in history during the reign of her brother Andronicus II. Palaeologus, when for the second time she was offered as a bride to the Mongolian prince, Charbanda, who then ruled in Persia,[478] the object of this new matrimonial alliance being to obtain the aid of the Mongols against the Turks, who under Othman had become a dangerous foe and were threatening Nicaea. With this purpose in view Maria proceeded to that city, both to encourage the defence of an important strategic position and to press forward the negotiations with Charbanda. The Despoina of the Mongols, however, did not comprehend the character of the enemy with whom she had to deal. Her contemptuous demeanour towards Othman, and her threats to bring the Mongols against him, only roused the spirit of the Turkish chieftain, and before the Greeks could derive any advantage from the 30,000 Mongolian troops sent to their aid, Othman stormed the fortress of Tricocca, an outpost of Nicaea, and made it the base of his subsequent operations.[479] The church was built for the use of a convent which the Despoina of the Mongols, like many other ladies in Byzantine times, erected as a haven of refuge for souls who had dedicated their lives to the service of God ([Greek: limena psychôn kata theon prosthemenôn bioun]). She also endowed it with property in the immediate neighbourhood ([Greek: peri tên topothesian tou Phanari]), as well as with other lands both within and beyond the city, and while Maria lived the nuns had no reason for complaint. But after her death the property of the House passed into the hands of Isaac Palaeologus Asanes, the husband of a certain Theodora, whom Maria had treated as a daughter, and to whom she bequeathed a share in the convent's revenues. He, as soon as Theodora died, appropriated the property for the benefit of his family, with the result that the sisterhood fell into debt and was threatened with extinction. In their distress the nuns appealed to Andronicus III. Palaeologus for protection, and by the decision of the patriarchal court, to which the case was referred as the proper tribunal in such disputes, the convent in 1351 regained its rights.[480] [Illustration: FIG. 95.--S. MARY OF THE MONGOLS. THE DOME.]