While his paternity is obscure, there is good evidence that he strengthened his claims to the throne by marriage to the Danish princess Christina Björnsdotter, a granddaughter of King Inge the Elder.

[10] Legend also attributes Erik with the initial spread of the Christian faith into Finland, "which at this time was pagan and did Sweden great harm".

Then one of his good men asked why he cried, since he should rejoice over the honourable victory which he had won over the enemies of Jesus Christ and the holy faith.

[15] If interpreted literally this might allude to conquests in Finland conducted by Saint Erik and Knut Eriksson (his grandfather and father).

The legend strongly accentuates Erik's personal piety: "This saintly king of ours conducted many godly prayers and sessions, as well as fasting.

He showed empathy with people in distress, was generous in giving alms to poor people, and forced himself to wear a shirt of horsehair, which he used when he was mortifying the flesh ... How he dealt with his secret enemy which is in the sexual parts, that is seen from the circumstance, that when he observed celibacy at fasting or religious celebrations, he often took a secret bath in a cold tub of water - even in wintertime - thus expelling non-permissible body heat with the cold.

"[12] While much of this may reasonably be regarded as hagiographical stereotypes, the scientific investigation of his remains shows that he consumed much freshwater fish, indicating observance of fasts.

Apart from Karl Sverkersson in Östergötland, the Danish prince Magnus Henriksen had a claim to the throne, being the great-grandson of Inge I and the great-great-grandson of King Sweyn Estridson of Denmark.

[22] Unbeknownst to the king, the allies gathered a considerable army and accosted Erik near Uppsala at Östra Aros when he attended Mass on the Feast of the Ascension in May 1160.

The king, being informed of the approach of the enemy, heard mass to the end, then armed himself and the few men at hand, and went out to meet Magnus' troops.

He was too soon put to death at an unfortunate moment, He always made good deeds while he was alive, and was therefore rewarded by God and his angels; his bones rest in Uppsala.

"[25] In a letter from 1172, Pope Alexander III complains that some people in Sweden had begun worshiping "a man who had been killed in debauchery and feasting".

Some scholars have assumed that this alludes to King Erik, and that the celebration of the Ascension Day was accompanied by feasting which enabled the surprise rebel attack.

In about 1167, as his son began to take power after the death of the latest Sverker king, Erik's body was enshrined, although there is no direct evidence for this until c. 1220.

[24] Facts and fiction about his life were inseparably mixed together, including the alleged miracle of a fountain springing from the earth where the king's head fell after being cut off.

In 1273, a century after Knut consolidated Sweden, Erik's relics and regalia were transferred to the present cathedral of Uppsala, built on the martyrdom site.

[31] The original medieval casket was melted down by Johan III, partly in order to pay off the Älvsborg ransom required by the Treaty of Stettin (1570) and to finance war against Russia.

The present Renaissance style casket was commissioned in the 1570s to contain his relics by Johan's Polish Catholic queen, Catherine Jagiellon.

[33][34] On March 19, 2016, researchers announced preliminary results that Erik's relics contained injuries consistent with legends of his demise, and that they would soon publish a detailed account.

According to the legend, King Erik the Saint was slain while he attended the Mass at the ecclesia Sancte trinitatis 'Trinity church' at Mons Domini.