He was married to Hildeburh, a sister of the Danish lord Hnæf, and was killed in a fight with Hnæf's lieutenant Hengest after Hnæf was himself killed by Frisians.
A passage from Beowulf as translated by Seamus Heaney (lines 1089–1090) reads:
"Finn, son of Folcwald,
should honour the Danes,..."
A possible reference to a lost tradition on Finn appears in Snorri Sturluson's Skáldskaparmál. Snorri talks of the animosity between Eadgils and Onela (which also appears in Beowulf), and writes that Aðils (Eadgils) was at war with a Norwegian king named Áli (Onela). Áli died in the war, and Aðils took Áli's helmet Battle-boar and his horse Raven. The Danish berserkers who had helped him win the war demanded three pounds of gold each in pay, and two pieces of armour that nothing could pierce: the helmet battle-boar and the mailcoat Finn's heritage. They also wanted the famous ring Svíagris. Aðils considered the pay outrageous and refused.