Click here to reveal spoilers for Dragon Age: Origins.
Gainley is encountered during The Trial of Crows. The Antivan Crows want him assassinated and the Warden can help by killing him themselves, thus undermining Loghain's attempt to gain Orzammar's support. If the Warden accepts the contract, Gainley and his cadre of guards attack the Warden on sight and are slain by the Warden's party.
↑The shields of the ambassador's bodyguards bear the heraldry of Gwaren, of which Loghain is teyrn. On top of that, the other assassination targets are known to serve Loghain or Rendon Howe.