Zareh was a male courier who lived during the 3180s. He had little regard for the United Federation of Planets (or "V'draysh", as he called it) and felt that nothing mattered after the Burn but hoarding dilithium.
Prior to 3189, he assumed the role of courier for "the Colony" by beheading the planet's previous courier. He supplied the planet's mining settlement with whatever it could not produce for itself, and held immense power over its Coridanite miners as a result. He also had experience with the planet's parasitic ice, and claimed to have seen it go down a person's throat on one occasion.
In 3189, his ship detected high-energy gamma rays and gravitational waves in the vicinity of the Colony, and subsequently found the time-displaced USS Discovery wrecked on the surface. He landed at the settlement to investigate and found Commander Saru and Ensign Sylvia Tilly trading dilithium to miners Os'ir and Kal in exchange for repairs to Discovery's transtator. Correctly deducing that Discovery had arrived from the past, and that Os'ir and Kal were planning to turn against him, Zareh took the group hostage and murdered Kal in retaliation.
Zareh planned to break down the Starfleet officers' equipment and sell their parts on the Tellarite Exchange, and demanded dilithium from Discovery's stores. He knew that the starship had come down on a glacier of the parasitic ice, and that Discovery would be crushed after sunset as the ice spread faster in the shade. He planned to send Tilly to collect the dilithium, reasoning that she stood a decent chance of making it there and back alive.
One of Zareh's henchmen caught Philippa Georgiou sneaking around outside the settlement, and brought her inside. Zareh tried to torture her into submission, but she brushed off his attempts. When he tried to have her killed, she and Saru fought back and killed Zareh's men, leaving him battered but alive. Zareh made a last-ditch attempt to sway Os'ir, threatening to destroy the settlement's life support and leave them to asphyxiate, but Os'ir refused and Tilly smashed a bottle on his head, leaving him dazed.
Georgiou attempted to kill Zareh with his own weapon, but Saru refused to allow this, as summary execution was against Starfleet's principles. Saru instead left the courier's fate to Os'ir, who opted to claim Zareh's ship and leave him exiled on the planet's inhospitable surface with only Tilly's pack to sustain him. (DIS: "Far From Home")
While stranded on "the Colony" Zareh lost some of his fingers on his left hand and the surrounding flesh was blackened due to the parasitic ice. He blamed Tilly for his mutilation.
Zareh was later part of Osyraa's boarding party when she hijacked Discovery. He was put as commander of the captured ship while Osyraa was speaking with Charles Vance. (DIS: "There Is A Tide...") After capturing Cleveland "Book" Booker, Zareh tortured him in Discovery's sick bay hoping to get the location of the dilithium nursery within the Verubin Nebula. However, he never got the information as both Book and Michael Burnham escaped his custody. Zareh confronted Book in an open turbolift and a fight ensued. Book came out victorious after Zareh insulted Book's cat Grudge; Zareh fell out of the turbolift to his death as Book shouted "[Grudge]'s a queen!" at him. (DIS: "That Hope Is You, Part 2")