He is one of the seven hunters in the game Metroid Prime: Hunters, which also include bounty hunter and main character Samus Aran. He is a spiritual being from the planet Vhozon with a quest to find the ultimate power. In one screen during the game, you see Noxus and Trace fighting in the icy world of Sic Transit. His weapon, the judicator will, when shot, bounce off of the walls before it disappears. It will also freeze his opponents temporarily. When he morphs, he turns into something that resembles a spinning top called the vhosythe.
Super Smash Bros. series
Noxus appeared as a trophy in Super Smash Bros. Brawl for the Wii that could be obtained through normal means. He and the other hunters in Metroid Prime: Hunters (including Samus) all had trophies in the game. The trophy description can be seen below:
"A bounty hunter and member of the elite Vhozon race. He seeks the ultimate power if only to ensure that no one else possesses it. Noxus uses the Judicator, an ice-beam weapon which, in addition to its offensive ice blasts, features a protective field that freezes opponents."