He was part of the Klingon Defense Force and assigned of the IKS 'Avwi. In 2370 he was part of the Klingon fleet that visited Deep Space 9 after a suspected attacked by the Cardassians almost brought the two powers to war. He was assigned by Captain Kol to the Federation Away team who was investigating the destruction of the IKS K'Tang.
He later help to prove it to be a Romulan plot, after he , Lieutenant commander Dax and Doctor Bashir discovered a secret Romulan base in the Gamma quadrant. (DS9 - Hearts and Minds comics: "For the Glory of the Empire", "On the Edge of Armageddon", "Into the Abyss", "Masters of War")
In 2371, he was part of the Klingon away party that responded to the Gakora colony distress signal. After the found a survivor, Kol ordered the Avwi back to DS9, once there he shared a drink with his friend, Bashir, to whom he admitted that he feared death during his captivity at the Romulan base. Koleth repaid his debt to Bashir when he placed himself in front of a phaser beam aimed at Bashir during an ambush. The shot proved fatal to Koleth who died sharing his last moments with Bashir. (DS9 comic: "Lightstorm")