Two years later he sought to live the life of a hermit, and moved out to the island of Croyland, now called Crowland (in present-day Lincolnshire), on St Bartholomew's Day, 699.

So great indeed was the abstinence of his daily life that from the time when he began to inhabit the desert he ate no food of any kind except that after sunset he took a scrap of barley bread and a small cup of muddy water.

The 8th-century Latin Vita sancti Guthlaci, written by Felix, describes the entry of the demons into Guthlac's cell:[4][5] [...] they were ferocious in appearance, terrible in shape with great heads, long necks, thin faces, yellow complexions, filthy beards, shaggy ears, wild foreheads, fierce eyes, foul mouths, horses' teeth, throats vomiting flames, twisted jaws, thick lips, strident voices, singed hair, fat cheeks, pigeon breasts, scabby thighs, knotty knees, crooked legs, swollen ankles, splay feet, spreading mouths, raucous cries.

For they grew so terrible to hear with their mighty shriekings that they filled almost the whole intervening space between earth and heaven with their discordant bellowings.Felix records Guthlac's foreknowledge of his own death, conversing with angels in his last days.

At the moment of death a sweet nectar-like odour emanated from his mouth, as his soul departed from his body in a beam of light while the angels sang.

Guthlac had requested a lead coffin and linen winding-sheet from Ecgburh, Abbess of Repton Abbey, so that his funeral rites could be performed by his sister Pega.

A year later Pega had a divine calling to move the tomb and relics to a nearby chapel: Guthlac's body is said to have been discovered uncorrupted, his shroud shining with light.

Another account, also dating from after the Norman Conquest, was included in the Ecclesiastical History of Orderic Vitalis, which like the Guthlac Roll was commissioned by the Abbot of Crowland Abbey.

The post-conquest accounts portray him as a defender of the church rather than a saintly ascetic; instead of dwelling in an ancient burial mound, they depict Guthlac overseeing the building of a brick and stone chapel on the site of the abbey.