This is a Qeynos Bounty quest, designed to raise faction with Qeynos after betrayal.
It starts by talking to Gil McMartin in Commonlands. Gil sends you to kill Torvis Nebarius in North Freeport. Use the Freeport Sewer system to navigate the city. Torvis spawns just north of the Sewer entrance near 7,-19,-246 as a single up arrow mob at the quest holder's level. Once dead, return to Gil McMartin in the Commonlands to collect your bounty.