Who is Grandpa Fool Bull from Lakota Woman and what is their importance?

Grandpa Fool Bull, also known as Uncle Dick Fool Bull, is a greatly respected man in the Native American community. Grandpa Fool Bull brings Mary to her first peyote meeting, where Mary takes a large quantity of peyote and experiences many visions. Over a hundred years old, Grandpa was present at the first Wounded Knee. Mary spends a great deal of time with Grandpa Fool Bull, who teaches her the old Indian ways.