L'sthwan was a human male who lived in the 24th century. A notorious criminal, he committed a number of violent crimes throughout the Alpha Quadrant. L'sthwan was wanted by a number of governments - including the United Federation of Planets.
In 2370, Starfleet posted a communique about L'sthwan. However the communique was very vague, and gave very little information about L'sthwan's physical characteristics. Lieutenant George Primmin was contacted about L'sthwan, and briefed Odo about this man. Odo dryly remarked that the vague communique resembled about half the customers at Quark's Bar.
Despite the fact that the communique was very vague, the station's crew became concerned that L'sthwan might be on the station when a Romulan female who arrived to play in the First Annual Deep Space Nine Poker Tournament was murdered while participating in a practice poker session. The crew soon deduced that L'sthwan had come to Deep Space 9 to play poker. Odo became convinced that L'sthwan would become violent again, and decided to play in the tournament himself. Despite objections from both Primmin and Quark, Odo entered the game.
L'sthwan was in fact present, operating under the alias of "Klar". Soon L'sthwan became convinced that one of the Ferengi players was cheating, and during a power outage took the opportunity to stab the other player with a knife. L'sthwan was arrested by Odo a few moments later. Doctor Julian Bashir was able to save the Ferengi's life, and when L'sthwan stated that because Ferengi cheated that genocide was in order Bashir decided to run psychological tests on L'sthwan. L'sthwan attempted to trade information on the real nature of spatial disruptions occuring in the area for his freedom to Commander Benjamin Sisko, however after giving the information Sisko ordered L'sthwan confined to security. (DS9 novel: The Big Game)