Snorri Sturluson wrote in the Ynglinga saga that Haki had amassed a great force of warriors and sometimes plundered together with his brother Hagbard (who himself was the hero of one of the most popular legends of ancient Scandinavia, see Hagbard and Signy). When Haki considered that he had amassed enough wealth and followers to make himself the king of Sweden, he proceeded with his army against the Swedish royal seat at Uppsala. Haki was a brutal warrior and he had twelve champions, among whom was the legendary warrior Starkad the Old.
The Swedish king Hugleik had also gathered a large army and was supported by the two champions Svipdag and Geigad.
On the Fyrisvellir (Fyris Wolds), south of Uppsala, there was a great battle in which the Swedish army was defeated. Haki and his men captured the Swedish champions Svipdag and Geigad and then they attacked the 'shield-circle' around the Swedish king and slew him and his two sons.
Haki and his warriors subdued the Swedish provinces and Haki made himself the king of Sweden. Then he happily sat in peace for three years while his warriors travelled far and wide and amassed fortunes.
The previous king, Hugleik, had two cousins named Eric and Jorund, who had become famous by killing Gudlög, the king of Hålogaland. When they learnt that king Haki's champions were gone plundering, they assembled a large force and steered towards Sweden. They were joined by many Swedes who wanted to reinstall the Yngling dynasty on the Swedish throne.
The two brothers entered Mälaren, went towards Uppsala, and landed on the Fyrisvellir. There they were met by king Haki, who had a considerably smaller force. Haki was, however, a brutal enemy who killed many men and lastly Eric, who held the banner of the two brothers. Jorund and his men fled to the ships, but Haki was mortally wounded.
Haki asked for a longship, which was loaded with his dead warriors and their weapons. He had the sails hoisted and set fire to a piece of tar-wood, which he asked to be covered with a pile of wood. Haki was all but dead when he was laid on top of the pile. The wind was blowing towards the water and the ship departed in full flame between the small islands out into the sea. This was much talked about and it gave him great fame.
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