Amrhein felt a drawn to become a member of a religious order, and was profoundly impressed by lectures at Tubingen on the role played during the middle ages by Saint Boniface in the spread of Christian culture.
On Pentecost, 1870 he made a retreat at the Benedictine Abbey of Beuron, and six months later entered the novitiate, taking the name "Andreas".
[2] Although he had mentioned his missionary hopes to Abbot Maurus, Amrhein soon learned that the contemplative life at Beuron did not provide for an active external apostolate.
He also met Gerard van Caloen, who later founded the St. Andrew's Abbey, Zevenkerken specifically to train monks for the missions.
Recalled to Beuron due to ill health, Amrhein served his abbey in various capacities during the hard times of the "Kulturkampf".
[2] In 1883 Amrhein made a pilgrimage to Rome and on the way visited in Steyl, Holland Arnold Janssen, founder of the missionary Society of the Divine Word.
While in Rome Amrhein discussed with members of Propaganda Fide his idea about a missionary society based on the Rule of St. Benedict.
Inspired by the lives of saints Leoba, Thekla, and Walburga, Amrhein also made provision for a convent of nuns at Reichenbach.
[4] In 1903, the publisher Benzinger of Einsiedeln commissioned a large painting of the Sacred Heart of Jesus, called "Iesus, Salvator Mundi".
The museum agreed to sell the painting to the Missionary Benedictine Sisters of Tutzing, a congregation founded by Amrhein.