Agne or Agni Skjafarbonde was a mythological king of Sweden, of the House of Yngling.
Agne being hanged by his wife SkjalfSnorri Sturluson relates that he was the son of Dag the Wise, and he was mighty and famous. He was also skilled in many ways.
One summer, he went to Finland with his army where he pillaged. The Finns gathered a vast host under a chief named Frosti (the Jotun Frosti who was the father of Snær the Old, and consequently Agne's great-great-great-great-grandfather).
A great battle ensued which Agne won and many Finns were killed together with Frosti. Agne then subdued all of Finland with his army, and captured not only great booty but also Frosti's daughter Skjalf and her kinsman Logi (in the older Ynglingatal only her kinsman, but in Heimskringla he was her brother, which seems to be a mistake by Snorri Sturluson).
Agne returned to Sweden and they arrived at Stocksund (Stockholm) where they put up their tent on the side of the river where it is flat. Agne had a torc which had belonged to Agne's great-great-great-grandfather Visbur (who, interestingly, was the son of Skjalf's niece Drífa). Although, they were related, Agne married Skjalf who became pregnant with two sons, Erik and Alrik.
Skjalf asked Agne to honour her dead father Frosti with a great feast, which he granted. He invited a great many guests, who gladly arrived to the now even more famous Swedish king. They had a drinking competition in which Agne became very drunk. Skjalf saw her opportunity and asked Agne to take care of Visbur's torc which was around his neck. Agne bound it fast around his neck before he went to sleep.
The king's tent was next to the woods and was under the branches of a tall tree for shade. When Agne was fast asleep, Skjalf took a rope which she attached to the torc. Then she had her men remove the tent, and she threw the rope over a bough. Then she told her men to pull the rope and they hanged Agne avenging Skjalf's father. Skjalf and her men ran to the ships and escaped to Finland, leaving her sons behind.
Agne was buried at the place and it is presently called Agnafit, which is east of the Tauren (the Old Norse name for Södertörn) and west of Stocksund, i.e. in what is still to this day called Agnehögen (Agne's mound) in Lillhersby.
Þat tel ek undr,
ef Agna her
Skalfar ráð
at sköpum þóttu,
þar gœðing
með gullmeni
Loga dís
at lopti hóf
svalan hest
Signýjar vers.[1] (http://www.home.no/norron-mytologi/sgndok/kvad/yngli.htm) How do ye like the high-souled maid,
Who, with the grim Fate-goddess' aid,
Avenged her sire? -- made Swithiod's king
Through air in golden halter swing?
How do ye like her, Agne's men?
Think ye that any chief again
Will court the fate your chief befell,
To ride on wooden horse to hell?(Laing's translation [2] (http://www.sacred-texts.com/neu/heim/02ynglga.htm))
Primary sources
Ynglingatal
Ynglinga saga (part of the Heimskringla)
Historia Norwegiae
Secondary sources
Nerman, B. Det svenska rikets uppkomst. Stockholm, 1925.