What is "kylfings"

The Kylfings ( Old Norse Kylfingar; Finnic Kylfingid; Hungarian Kölpények; Old East Slavic Колбяги, Kolbiagi; Byzantine Greek Κουλπίγγοι, Koulpingoi; Arabic al-Kilabiyya) were a people of uncertain origin active in Northern Europe during the Viking Age, roughly from the late ninth century to the early twelfth century. They could be found in areas of Lapland, Russia, and the Byzantine Empire that were frequented by Scandinavian traders, raiders and mercenaries. Scholars differ on whether the Kylfings were ethnically Finnic or Norse. Also disputed is their geographic origin, with Denmark, Sweden and the Eastern Baltic all put forward as candidates. Whether the name Kylfing denotes a particular tribal, socio-political, or economic grouping is also a matter of much debate.

They are mentioned in Old Norse runestone inscriptions, sagas (most notably in Egil's Saga), and poetry (such as Thorbjorn Hornklofi's poem Haraldskvæði), as well as Byzantine records and Rus' law-codes. According to the sagas, the Kylfings opposed the consolidation of Norway under Harald Fairhair and participated in the pivotal late ninth century Battle of Hafrsfjord. After Harald's victory in that battle, they are described in the sagas as having raided in Finnmark and elsewhere in northern Norway and having fought against Harald's lieutenants such as Thorolf Kveldulfsson.