No'Mat was a location, known for its lava caves, in the mountains of the planet Qo'noS. These caves played a role in the Rite of MajQa wherein a young Klingon while meditating would experience a vision. This vision, or hallucination depending upon one's interpretation, might play a role in the Klingon's future. (TNG: "Birthright, Part I" , "Rightful Heir" ; DS9: "The Sword of Kahless")