Spoiler warning: Plot and/or ending details follow.
Marab, son of K'Vagh was a male Klingon who had lived in the 22nd century who became a QuchHa' Klingon after 2154. He had been an officer in the Klingon Defense Force. He was the son of General K'Vagh, son of Wor'maq.
When he came of age he entered into the Klingon Defense Force, however at his request he received no special treatment from his father. In 2154 Marab was stationed on the Qu'Vat colony. He was selected to be one of the first to have Dr. Antaak to inject him with the Qu'Vat virus - which contained Augment DNA. This caused him to lose his forehead ridges and gain a more human like appearance. He was one of the Klingons selected by his father to participate in a raid on the Enterprise (NX-01) under the command of Lieutenant Laneth. Despite the Klingon attempt to destroy the Enterprise by accelerating the ship to the point where the warp core would breach, Chief Engineer Trip Tucker was able to shut down the engine and purge the Klingon programming.
During the raid Marab was wounded and then captured by the Enterprise crew. He was imprisoned next to Malcolm Reed, who had been placed in the brig by Captain Jonathan Archer after betraying his trust. Reed tried to convince Marab to help the Enterprise crew, but he was unsuccessful. When Marab became ill due to the Qu'Vat virus injections, Archer convinced Marab to help them as it was the best way to help his people. Upon arrival at Qu'Vat Archer released Marab to his father. Enterprise CMO Doctor Phlox was able to develop a cure, however the cure did not reverse the physical changes the virus had already caused, leaving Marab and several hundred million other Klingons with more human-like features. (ENT episode: "Divergence")
Marab and the others would eventually become known as QuchHa'. As uninfected Klingons - who were called HemQuch - began to persecute their QuchHa' brethren the QuchHa' Klingons began fighting back. Some time prior to 2165 Marab was killed in battle against the HemQuch . (ENT - Rise of the Federation novel: Live by the Code)