Annorax was the creator of the Krenim Temporal Weapon Ship. After its first use as a weapon, Annorax soon discovered the dire consequences of eliminating something from history; he obliterated much of the Krenim Imperium as well, including his own wife. He became obsessed with bringing her back, and directed his crew to continue obliterating specifically chosen targets from history, hoping to restore the Imperium- and his wife.
Annorax strove for hundreds of years towards this end, eventually coming to regard Time itself as an enemy he could not defeat. However, after Annorax came into conflict with the crew of the U.S.S. Voyager, he captured Chakotay and Tom Paris and tried to sway them to his side. Chakotay came to admire him to a degree, but eventually aided Paris and dissident members of Annorax's crew in sabotaging the Weapon Ship. Kathryn Janeway crashed the Voyager into the temporal core of the ship, wiping the ship from history and restoring all that had been altered to the way it was.
Annorax, no longer interested in building the Temporal Weapon Ship in the revised history, continued to live a happy life with his wife.