When Duke Wartislaw IX of Pomerania-Wolgast died in 1457, his will named not only his sons Eric II and Wartislaw X, Otto's stepfather, as heir, but also young Otto III. An inheritance dispute arose, is which Frederick II supported Otto, and also used the opportunity to meddle in the affairs of Pomerania.
In 1460, Otto III was declared an adult, at the request of the Estates of Pomerania. This ended the regency by Brandenburg; instead the 15-year-old Otto III took up government himself. The most important offices in his court were occupied by Brandenburg-minded people. The disputes about the inheritance of Warislaw IX were settled in 1463, with Otto receiving Pomerania-Stargard, the western part of Pomerania.
Otto died of the plague on 7 September 1464 and was buried in the Otten Church in Stettin. He was unmarried and had no children. With his death, the Pomerania-Stettin line of the House of Griffins died out. It had begun with Duke Otto I (c. 1279-1344).
Otto's death triggered the Stettin War of Succession. Elector Frederick II claimed that Pomerania-Stettin was now a completed fief and that it should fall back to Brandenburg. The Dukes in Wolgast claimed that it was a part of Pomerania and should fall to the surviving line of the House of Griffins.
According to legend, the dispute began when Otto was buried. Mayor Albert Glinde of Stettin is said to have put Otto's helmet and shield in his grave, to indicate the end of his dynasty. A gentleman from Eickstädt then jumped into the grave and took the helmet and shield out again, with the words "We still have hereditary, born rulers, the Dukes in Wolgast. The helmet and shield belong to them."
