Swietopelk II prevailed, his son Mestwin II, duke in Pomerelia from 1266, however again had to deal with claims raised by the Pomeranian Griffins and also by his brother Wratislaw II. To secure his rule, Mestwin accepted the suzerainty of the Ascanian margraves of Brandenburg by the 1269 Treaty of Arnswalde, but later on, in 1282, Mestwin and Polish Duke Przemysł II signed the Treaty of Kępno, which transferred the suzerainty over Gdańsk Pomerania including Sławno to Przemysł II. Upon Mestwin's death in 1294, the Samborides became extinct and Sławno was reintegrated with Poland. In 1308 Brandenburg invaded the region and Waldemar of Ascania finally separated Sławno from Pomerelia, which he sold to the Teutonic Order by the 1309 Treaty of Soldin. He nevertheless lost the town to the Griffin duke Wartislaw IV of Pomerania in 1317, whereafter Sławno remained a part of the Griffin-ruled Pomeranian duchies until 1637.