The lord of the Grim Legion, victims of Violence, the Smiling Lord is also Stygia's foremost traitor, having sold out his master to Yu Huang in exchange for a position of authority over the Western Dead.
The Smiling Lord, who is apparently the second to hold this title, is one of the "big three" deathlords, meaning that he oversees one of the largest legions. As a result, he is engaged in a perpetual power struggle with the Ashen Lady and Skeletal Lord for the control of Stygia. The Smiling Lord has adopted to this role by exploiting the skills and circumstances of his dead.
The Grim Legion, by its nature has a large number of trained killers. In addition, by its nature, everyone in the Grim Legion was killed by somebody. The Smiling Lord gives every wraith who crosses the Shroud a personal promise that good service will be rewarded by an opportunity to even the score. The Smiling Lord, as a result, also has his fingers in a lot of "score-evening" organizations, such as the Proctors and the Puppeteers - if he's willing to join up with Stygia's greatest enemy, guilds are small potatoes after all.
The Smiling Lord had a dry-run for his treason during the Great War, when he openly declared himself the new emperor of Stygia. The resulting violence continued until Charon (then in hiding for his own reasons) intervened with the Mnemoi. For reasons unknown to anyone except Charon and the Lady of Fate, the Smiling Lord was then spared - perhaps because Charon would need a Judas in his personal passion play.