Religious Beliefs. A pervasive underlying supernatural power was seen primarily in natural phenomena, which were personified and at times deified. The Kiowa revered the Sun, constellations such as the Pleiades, and natural forces such as the Cyclone, and gave special respect to the bison, bear, and eagle. Sendeh (or Sainday) is the main protagonist in Kiowa tales, as both culture hero and trickster; he has human rather than animal attributes. Spider Woman, Twin Heroes (Split Boys), and Coyote, suggestive of Southwestern affinities, appear in origin and explanatory tales. Personified natural forces and animal spirits were encountered in visionary experiences. Individuals sought power through the Sun Dance and personal visionary experiences. The Taime, an anthropomorphic effigy; medicine bundles; and several other fetishes were prominent in hunting, curing, and purification rites. In 1873, Quaker mission efforts began among the Kiowa, followed by Methodist, Baptist, and other denominations. The Native American Church also increased in importance as the Sun Dance and other hunting and war ceremonies declined. Protestant affiliation is now the norm; however, traditional practices continue and have experienced revival. As in earlier days, tribal ceremonies are concentrated in the summer, now centered on July 4.
Religious Practitioners. The Taime and medicine bundle priests were subject to numerous taboos and requirements of circumspect behavior. The Taime was housed in a special tipi and carried in public display by its priest; a select group of men, who had received visions, assisted him. Owners of the ten medicine bundles were called upon to intervene in disputes and could give sanctuary. Buffalo doctors were especially qualified to treat illness attributed to violation of taboos on the bear.
Ceremonies. The Sun Dance was held annually until 1887 when it was prohibited by the government and halted by military force. Other traditional dances, such as those of the warrior societies, also performed in the summer season, are now part of the July 4 celebration. A scalp dance followed the return of men from war; curing ceremonies were held at any time. The Feather Dance, the Kiowa response to the Ghost Dance movement, became institutionalized as the Invisible 00Church and held semiannual dances until prohibited in 1916; beliefs and iconography were a blend of Kiowa tradition and Christian influences. Some vestiges of this movement carried over into sectarian Christian churches. Peyotism now follows the pan-Indian ceremonialism of the Native American Church.
Arts. Tipi covers were often decorated with designs that symbolized the accomplishments of the owner; these designs, handed down through generations of the same family, constituted a type of heraldic emblem. The painted designs of Sun Dance shields also had symbolic significance, related to membership in warrior or medicine societies. Calendar histories, painted on buffalo hide, depicted important events of successive summer and winter periods; these are a valuable source of information about the nineteenth-century Kiowa. More recently, individual Kiowa have shown remarkable talent in graphic arts; a group known as the "Kiowa Five" (Spencer Asah, Stephen Mopope, Jack Hokeah, James Auchiah, and Monroe Tsatoke) became internationally recognized early in the present century, setting a pattern for Kiowa successes in the arts; literary artists include the poet N. Scott Momaday. Kiowa craftsmen have been active in the production of jewelry and silverwork based on traditional designs and marketed through the Oklahoma Indian Arts and Crafts Cooperative.
Medicine. The sweatbath was used for curing and for ritual purification. Ill health as well as misfortune was often seen as the result of supernatural harm or the violation of taboo. Certain older women served as herbalists and midwives, assisting with difficult births. Buffalo doctors and other curers received power through visionary experiences; shamanistic methods were used in healing.
Death and Afterlife. The elderly and disabled were abandoned if they could no longer travel. Mourning involved slashing of clothing, gashing the skin, cropping the hair; women might amputate finger joints. The dead were buried, preferably in a remote, isolated spot. Personal property of the deceased was destroyed and the name tabooed, unless bestowed on an heir before death.
Richard Hollingsworth
Still, I can't confirm definitively and the phrase is prominent in the film. I suspect it was brought in for the poetry of it.
I think Kiowa religious traditions and myths did include life after death, as they had taboos about mentioning the names of the dead. I gather that they had similar story-telling motifs to those of many other tribes, notably the trickster character. This doesn't mean that they all believed in myths -- I always find it funny when it's assumed that all pre-modern individuals swallowed their culture's superstitions hook, line and sinker.