Mystic Warriors (Mystic Series #3)
Rosanne Bittner

But all is not well. White hunters have stolen the sacred white robe and great misfortune has befallen the Lakota. Settlers continue to invade Lakota territory, backed by vicious cavalry forces that massacre women and children. The Lakota are starving and their anger is growing.
Led by Rising Eagle, a great force of Lakota and other tribes wage war upon the white man. Together they battle to regain the land stolen from them, to protect the precious buffalo the white man wantonly destroys, and to search for the sacred white robe.