The Pahvans were intelligent beings native to the planet Pahvo in the Beta Quadrant, manifesting as clouds of glowing blue particles. They existed in total harmony with their world, described as a "symbiosis between nature and the living spirit". As such, they did not register on tricorders as lifeforms separate from the forests on Pahvo. Their language was indecipherable to the universal translator, and they had the ability to transport individuals through what appeared like teleportation.
Since the dawn of their existence, the Pahvans wished to contact others not from their world and share of themselves. They controlled a massive crystal transmitter, which broadcast into space the distinctive "music" created by the planet.
On stardate 1308.9, a USS Discovery away team consisting of Commander Saru, Specialist Michael Burnham, and Lieutenant Ash Tyler made first contact with the Pahvans during a mission to modify the Pahvan transmitter to detect cloaked Klingon ships. Saru was able to establish communication with the Pahvans, though he was distressed by the planet's constant sound. To aid him, the Pahvans infiltrated his body and gave him harmony, freeing him from the fear that the Kelpien had felt all his life.
Unfortunately, this newfound peace led Saru into a fight with Burnham and Tyler, as he desperately wanted to prevent them from bringing Discovery, and therefore the Federation-Klingon War, to Pahvo. Upon witnessing the altercation, the Pahvans decided to help the Federation and the Klingons find harmony. They repaired the signal inhibitor the Starfleet team brought, and used it in conjunction with their crystal transmitter to send an invitation to Pahvo on Federation and Klingon frequencies. Kol received the transmission and took the Sarcophagus to Pahvo. (DIS: "Si Vis Pacem, Para Bellum")