He was hired prior to the Interregnum by the Sorceress in Green as part of the conspiracy to arrange the set-up of a false genescan of Norathar e'Lanya in order to discredit Norathar's family. He might also have been hired to perform the murder of Norathar's parents during their assault on Dzur Mountain.
Some 200 years after the Interregnum, this involvement caused him to also be later tasked with killing Baritt, so as to prevent Baritt's qualms from breaking the conspiracy, and so as to position Sethra the Younger to be made Warlord.
Laris was heavily involved in the turf war between K'tang the Hook and Welok the Blade, and may have actually run the war (for Welok). It is rumored that Laris himself gave Welok control of his area after this war was over. Presumably, Laris was in this position due to his connections with the Sorceress in Green.
Later, Laris started a turf war with Vlad Taltos, as a part of the continuation of the Sorceress' plot, so as to discredit the current Dragon Heir (Aliera e'Kieron), and two of her potential successors (Norathar e'Lanya and Morrolan e'Drien).
Laris was killed by Vlad, after Vlad discovered and countered the conspirators, and Laris lost the support of the Sorceress in Green.