In 1377, he became a Duke of Pomerania, ruling in Pomerania-Stolp; at times he was its co-ruler with his brother, Bogislaw VIII.

[3] On 1 August 1392, Wartislaw, his brother Bogislaw VIII and some clergy of the Bishopric of Cammin met with Johann, the bishop of Lebus, and Johann of Görlitz, a prince of the Margraviate of Brandenburg, in Brandenburgian Landsberg an der Warthe (now Gorzów).

[4] During Wartislaw VII's absence, the Pomeranian noble Matzke von Borcke auf Stramehl had led a holdup in Pomerania-Stolp, where Bohemian komtur Johann von Mühlheim was robbed on his way to the Teutonic Order state in late 1392.

Konrad von Wallenrode, Grand Master of the Teutonic Knights, protested at Wartislaw VII's and Bogislaw VIII's court and demanded satisfaction.

Wartislaw and Bogislaw then granted him permission to destroy Matzke's residence Stramehl, which eventually was razed.