Theodore was capable and extremely ambitious. Notwithstanding his oath to Laskaris, he aspired not only to expand his state at the expense of Thessalonica, but to eventually recover Constantinople and revive the Byzantine Empire with himself as its ruler. To secure his northern flank, Theodore allied himself with Serbia and the Albanian clans. The Principality of Arbanon had already come in the Epirote political orbit under Michael I, and closer ties developed when its ruler, Demetrios, died in 1215, leaving his principality to his widow, who promptly remarried the next year to a Greek magnate, Gregory Kamonas. Against the Serbs, Theodore abandoned Michael I's attempt to pursue a northward expansion into Zeta, and instead pursued an alliance with the Serbian prince Stefan II Nemanjić () that was directed towards keeping the Bulgarians in check. The ties between Epirus and Serbia were solidified by the marriage of Theodore's brother Manuel Komnenos Doukas to one of Stefan II's sisters . Stefan II then sought to wed one of his sons—in all likelihood his eldest son and heir, Stefan Radoslav—to Michael I's second daughter Theodora. The Archbishop of Ohrid, Demetrios Chomatianos, refused to sanction the marriage due to consanguinity—Theodora was a second cousin of Stefan Radoslav's mother, Eudokia Angelina, a daughter of Alexios III Angelos. In 1217, Stefan II tried to circumvent this by suggesting himself as the groom to Theodora's half-sister Maria, but Chomatianos vetoed this proposal as well on similar grounds. Finally, Stefan Radoslav married Theodore's firstborn daughter Anna in winter 1219/20.