In 2258, N'Grath seems like a very significant figure in the criminal underworld of Babylon 5. He was involved in trading weapons, hitmen, bodyguards, and several other vices.
His first appearance was in the Episode Soul Hunter, where he is seen giving the Titular character a map of Babylon 5. He was than hired by Trakis to provide him with enough men to distract Commander SInclair. N'grath is next seen being hired by Narn Ambassador G'kar, who needed a body guard to protect him from Tu'pari . N'grath's final appearacne sees him refusing to negotiate with security officer Michael Garibaldi, as he recognzes him as an officer of the law.
After this, N'Grath was "taken down" off-screen. In 2262, a human criminal named Trace attempted to fill the vaccum that N'Grath left behind, only to fail.
N'Grath is a memeber of an unkown, arthropodic race. He breathes a combonation of gasses taht cannot be used by humans(though they can by some other races who can breathe in Earth-Reguar oxygen).