As a medicine man, Black Elk had prepared to visit a dying boy in the village, only to encounter a Jesuit priest praying there first. He encountered a power greater than his own, and accepted an invitation to spend time at the mission. He was baptized and took the name Nicholas shortly after. As a Catholic Catechist (an often downplayed aspect of his life), he was widely considered an apostle to the plains Indians. Thousands of people were brought to faith – both Indian and non-native, through his work and famous preaching.
His primary work was with new converts and as an evangelist alongside the priests — when priests were not available his duties included baptizing and burials. His passion for Christ as the Creator and fulfiller of things drove him to vigorous and passionate study. Nick thought that many of the Lakota spiritual traditions had come from God to teach them to live in a good way and that Christ made sense of all of it. Many experts agree that his practice of the Christian faith, life, and mission were well-integrated with his worldview and practice as a Lakota.
One such integration is the change in the symbolism for the sun dance ceremony. Traditionally, it was a time of fasting, prayer, and suffering in order to attain personal power for victory in battle. It has become, and many credit Nicholas Black Elk for this shift, a ceremony of prayer and fasting on behalf of all the people – including enemies. For Nick, it was a ceremony to remind the people of the suffering and death of Christ for all of creation.
Source: August 19 – Nicholas Black Elk – Celebrating Our Transhistorical Body