In addition to the Swedish heartland around lake Mälaren it may have extended down along the Baltic Sea as far south as Blekinge.

According to the Flateyjarbok, his success was largely due to an alliance with free farmers against an earl-class nobility, but archaeological findings suggest that the influence of that class diminished during the last part of the tenth century.

In all probability he also founded the town of Sigtuna, which still exists and where the first Swedish coins were minted for his son and successor King Olof.

[14] Eric the Victorious is named in a number of sagas, Nordic tales of history preserved from oral tradition.

One saga describes his marriage to the infamous Queen Sigrid the Haughty, daughter of a legendary Viking, Skagul Toste, and how in their divorce he gave her all of Gothenland as a fief.

The first expressly mentions how an Eric has utterly defeated an enemy host at a fortification at Fýrisvellir, while the second specifies that the Vikings were superior in numbers but nevertheless were handily captured when they attacked Sweden, and only those who fled survived.

The runestones of Hällestad and Sjörup in Scania, then a part of Denmark, do mention a battle at Uppsala characterized by the defeat and flight of the attackers.

Saxo unlike Adam of Bremen mentions that Eric defeated Sweyn Forkbeard's army decisively in a battle in Scania for the throne of Denmark.

For some years nothing happened and Åke had a son Edmund, father of Ingvar the Far-Travelled, leader of the Rus expedition to the Caspian Sea.

After that Eric started a purge where all jarls allied with Åke were mercilessly killed and their property was confiscated.

[19][20] German ecclesiastic chronicler Adam of Bremen (around 1075) provides by far the oldest narrative about King Eric, and it differs substantially from the sagas.

He does not mention the Battle of Fýrisvellir but relates that Eric gathered a large army and invaded Denmark against King Sweyn Forkbeard.

[27] After his victory, Eric kept Denmark for a time, while Sweyn was forced to flee, first to Norway, then to England, and finally to Scotland whose king received the refugee with kindness.

Another Viking detachment was tricked deep into the desolate marsh of Glindesmoor by a captured Saxon knight and annihilated by pursuing Germans.

Due to that significant event, missionaries were allowed to sail over from Denmark to Sweden where they "worked valiantly in the name of the Lord".

[30] Adam's account seems to date the death of Eric the Victorious between 992, when the accession took place in Poland of his ally Boleslaw I (above), and 995, when his son Olof's coinage began in Sigtuna.

Discrepancies between Adam's account and other sources have led to a variety of interpretations among Swedish historians, especially about Eric's marriages.

[31] According to a recent evaluation by Harrison, the conquest "is not unlikely, at least if we consider it a loose suzerainty over powerful Danish lords".