After his father Christopher I died, his mother Margaret Sambiria ruled Denmark in his name until 1266, proving to be a competent regent.

Immediately, she had to fight to keep her son on the throne from two powerful enemies; Archbishop Jacob Erlandsen (ca.

[3][4] Taking advantage of the situation, Chief Jaromar II of Rügen (c. 1218–1260) gathered an army of Wends and invaded Zealand.

The combined forces defeated Queen Margaret in 1261 at the Battle of Lohede south of Danevirke in Schleswig-Holstein.

She and her son were captured and were forced to cede royal properties in southern Jutland to secure their release.

[6] In 1260, Queen Margaret had released Archbishop Jacob from prison thinking he would be grateful, but he subsequently issued an interdict over all of Denmark trying to force her and Eric off the throne.

In 1263, acting as regent of Denmark, the queen wrote to Pope Urban IV asking him to intervene with Archbishop Jacob.

[7] The King signed the charter at Nyborg Castle, recognized as Denmark's first-ever constitution in existence.

[8][9] Legend has it that several nobles swore an oath that they would murder Eric in revenge for personal slights or policies the king enforced that they did not like.

Chief among the conspirators was marshal (Danish: marsk) Stig Andersen Hvide and Jacob Nielsen, Count of Halland.

The assassins, dressed as Franciscan friars, were kept informed as to the king’s whereabouts and waited for everyone to settle down for the night.

[14][dubious – discuss] The court immediately blamed the nation's most powerful noblemen Stig Andersen Hvide and Count Jacob of Halland and outlawed them and seven others.