of Ancient Estonia featured numerous hillforts, some later hillforts on Saaremaa heavily fortified during the Viking Age and on to the 12th century. There were a number of late prehistoric or medieval harbour sites on the coast of Saaremaa, but none have been found that are large enough to be international trade centres. The Estonian islands also have a number of graves from the Viking Age, both individual and collective, with weapons and jewellery. Weapons found in Estonian Viking Age graves are common to types found throughout Northern Europe and Scandinavia. Curonians The Curonians were known as fierce warriors, excellent sailors and pirates. They were involved in several wars and alliances with Swedish, Danish, and Icelandic Vikings. In , according to Norna-Gests þáttr saga from , Sigurd Hring ("ring"), a legendary king of Denmark and Sweden, fought against the invading Curonians and Kvens (Kvænir) in the southern part of what today is Sweden: "Sigurd Ring (Sigurðr) was not there, since he had to defend his land, Sweden (Svíþjóð), since Curonians (Kúrir) and Kvænir were raiding there." Curonians are mentioned among other participants of the Battle of Brávellir. Grobin (Grobiņa) was the main centre of the Curonians during the Vendel Age. Chapter 46 of Egils Saga describes one Viking expedition by the Vikings Thorolf and Egill Skallagrímsson in Courland. According to some opinions, they took part in attacking Sweden's main city Sigtuna in 1187. Curonians established temporary settlements near Riga and in overseas regions including eastern Sweden and the islands of Gotland and Bornholm. Scandinavian settlements existed along the southeastern Baltic coast in Truso and Kaup (Old Prussia), Žardė (Western Lithuania) and Grobin (Courland, Latvia). Eastern Europe The Varangians or Varyags were Scandinavians, often Swedes, who migrated eastwards and southwards through what is now Russia, Belarus, and Ukraine mainly in the 9th and 10th centuries. Engaging in trade, piracy, and mercenary activities, they roamed the river systems and portages of Gardariki, reaching the Caspian Sea and Constantinople. Contemporary English publications also use the name "Viking" for early Varangians in some contexts. The term Varangian remained in usage in the Byzantine Empire until the 13th century, largely disconnected from its Scandinavian roots by then. Having settled Aldeigja (Ladoga) in the 750s, Scandinavian colonists were probably an element in the early ethnogenesis of the Rus' people, and likely played a role in the formation of the Rus' Khaganate. The Varangians are first mentioned