The fifteen-year-old Johan Sverkersson from the rival House of Sverker was hailed king by the Swedish aristocracy,[6] while Queen Rikissa returned to her Danish homeland where her brother Valdemar Sejr ruled.

[7] Erik spent his early youth in Denmark, while Valdemar championed his rights to the Swedish throne and tried to prevent the coronation of Johan.

[9] The battle is believed to have taken place in Olustra (Ostra) in Södermanland, although Alvastra in Östergötland has been mentioned as a possible site.

Knut Långe was crowned King of Sweden in 1231, but his time was short and he died in 1234, which prompted Erik to return to the throne.

The Swedish Erikskrönikan on the contrary asserts that he came back after King Knut's death, after a new round of fighting;[15] however, this is not recorded in any other source.

The Folkung Ulf Fase, who had been Jarl of the realm under Knut Långe, continued to serve in that function under Erik.

As a king, Erik is depicted in Erikskrönikan as good-natured but physically passive: He readily supported what was right and reasonable, and loved his own kindred.

While Ulf pursued a policy of alliance with the Norwegian king, Birger strove to strengthen royal authority by allying closely with the Catholic Church.

[19] Sweden had a certain presence in southwest Finland by the early 13th century, although it is unclear to what extent this translated into political power.

The Erikskrönikan contains a graphic description of a military expedition to Tavastia (Finnish: Häme) further to the east that King Erik dispatched in an unspecified year, possibly in 1238–39 or 1249–50.

A fleet of ships commanded by a certain Spiridon and accompanied by a few bishops went up the Neva River, but were attacked and routed by the Novgorodian prince Alexander Nevsky.

The Folkung Party warred with King Erik and Birger, but their peasant allies in Uppland lost the Battle of Sparrsätra and were punished by tightening royal taxation.

The Folkung leader Holmger Knutsson, a son of Knut Långe, fled to Gästrikland but was captured by Erik's men and beheaded.

On behalf of Pope Innocent IV, he urged the Swedes to stick to canonic-juridical praxis as laid down by Rome.

With him the House of Erik became extinct in the male line, with the possible exception of Knut Långe's son Filip (d. 1251).