Uŋktéhi, the great water monster, is a horned serpent-being of the deep waters and the chief of the underwater powers — wakȟáŋ but dangerous, bringer of floods and drownings. She is the eternal enemy of the Thunderbird Wakíŋyaŋ, who hunts her with lightning; this opposition of water and sky is a fundamental polarity of Lakota cosmology, and the fossil bones of the Plains were taken for the remains of the Uŋktéhi the Thunder had slain.