PreRussia - стр. 7

Further, the Joachim Chronicle and the "Legend of Slovene and Rus" diverge somewhat. According to the legend, Gostomysl had two sons, but both of them did not survive their father. Therefore, Gostomysl had no one to transfer power to. Civil strife was brewing. Then, just before his death (in 844), the prince ordered to send envoys "across the sea to the land of Prussia" so that they would ask for a ruler from the family of Caesar Augustus. And so it was done. Rurik was invited. Note that Gostomysl sends an ambassadors to Prussia for some reason not by land, but by sea. The legend is largely consonant with the "Lomonosov theory", since Rurik was invited from somewhere in Prussia (although the Vistula and Dvina rivers are not mentioned), albeit Rurik is not the grandson of Gostomysl here.

By the Joachim chronicle, Gostomysl had four sons and three daughters, but all his sons either died in the war or of illness, and all the daughters were married to neighboring princes. One his daughters, Umila was married to one of the West Slavic princes from the island of Rugen (now in Germany, in old slavic – “Rujan”) and gave birth to three sons. Rurik, the eldest of them, was invited by Gostomysl to the Grand duchy in Novgorod in order to observe dynastic succession, the legality of power and prevent civil strife. Rurik came along with his brothers. The chronicle in the main also does not contradict the "Lomonosov’s theory", except that the grandson Rurik was invited not from the place of residence of the Rosses near the Rus River between the Dvina and the Vistula in Prussia, but from the then Slavic island of Rujan (Rugen).

The Rugs (Rujans in slavic) are often mentioned in foreign chronicles and the island Rugen is located just next to Prussia. At that time the island was inhabited by militant pagan Slavs who worshipped their gods in the Arkone temple in the city of the same name. Thus it becomes clear why Gostomysl sent ambassadors to Prussia "across the sea" according to the Joachim Chronicle. He probably sent them to Rugen.

Here is how the early medieval chroniclers described the Rujan Slavs: "… these are cruel people that live in the heart of the sea and are overly devoted to idolatry. They excel among all Slavic tribes; have a king and a famous sanctuary. (…) completely neglecting the benefits of agriculture, they always ready to make attacks on the sea, laying their only hope and all their wealth on ships. That is, the Rujans led the real Varangians’ (Vikings’) way of life.