Missionaries
In Redbad's age, Christian missionaries went out to battle 'heathen superstitions'. However, the worship of these gods and nature was rooted deeply in Frisia. Sacrilege was punishable by death by sacrifice. Many missionaries have been to Frisia.
Willibald
The priest Willibald descibed in disgust how Redbad destroyed churches, drove clergy out, and built new shrines dedicated to pagan gods. These descriptions are probably no Frankish exaggerations. Multiple sources, including personal letters, confirm Redbad's war against Christianity.
Willibrord
In 695 CE, Willibrord is appointed 'archbishop of the Frisians' by the pope. The accounts about the life of archbishop Willibrord tell of how a violent storm caused him to land on Fositesland around 700 CE: Redbad's holy island. He and his monks desecrated the holy well and slaughtered animals. The 'heathen king Redbad' was furious. By way of casting lots, a special ritual, it is decided whom of the Christian culprits is sentenced to death.
The accounts of Willibrord's life are from a Christian perspective. Willibrord knew the animals and the well were holy to the Frisians, but he 'cared little for the foolish religion of this place, nor the savage nature of the king'. His deeds were meant to prove this 'heathen' faith was heresy.
Bonifatius
This missionary went from England to Frisia only after Redbad's death. He meant to go before, but politics prevented him from doing so; in 716 CE Pepin had just died, causing a Frankish civil war and Redbad to once again try to grow in power.
Redbad was not particularly liked by Christian clergy. Bonifatius even received a letter of congratulations from a friendly Anglo-Saxon nun after Redbad's death. In this letter, she considers him lucky with the death of 'Rathbod, enemy of the Catholic church.'
Vitae
The lives of many missionaries have been recorded. These are important records where Redbad's name is mentioned. The most important examples are the Vita Wulframni, VIta Willibrordi, Vita Erminonis and the Vita Bonifatii, of Saints Wulfram, Willibrord, Erminus and Bonifatius respectively.
The story of the baptistry
There is a story where Christian try one last time to baptise Redbad, but in vain. The Frisian king chooses his ancestors' religion and the pagan Walhalla above the Christian heaven.
This last act of resistance told in song, probably soon spread around Frisia. Years later, missionaries try to frame the failed baptism in a more Christian-favoured light in the Vita Wulframni. In it, it is told how Redbad was deceived by the devil, who in a dream promised him a beautiful golden throne in Walhalla.