Ferdinand Sertl was the leader of the Steyr town band and looked after the fire-watchers on the town parish tower. As he suffered from epilepsy, he liked to be alone. He could be in a small wood in Unterhimmel (that is "Under the heavens"). In 1695 he paid 30 kreuzers to a nun of the Coelestine order in Steyr for a small wax image of the Christ-Child (in German, Christkindl) and gave it a home in the trunk of a spruce tree in a hollow hacked out for the purpose. Sertl now made a pilgrimage several times a week to his tree. He soon had no more epileptic fits and attributed this to his devotions. Although he wanted to keep everything secret, the place soon had such a stream of visitors that a wooden chapel was erected in 1699 around the tree. Abbot Anselm began with the building of the present church in 1702 with the Italian builder Giovanni Battista Carlone. To succeed him after his death Abbot Anselm immediately engaged the famous Baroque builder, Jakob Prandtauer (1660-1726).
Around 1720 the altar received a towering superstructure of carved and gilded wood around the preserved trunk of the "Christ tree" to which Sertl once committed his miraculous image.