Reining It In

Acquisition
Reining It In is acquired during Act 3 of the main storyline. As you travel about the Docks at night, you will encounter various groups of slave hunters who will attack you on sight. Eliminate enough of these groups, and the location of their base will be revealed, marking the start of this quest.

Walkthrough
Once you have received the quest, there should be a marker on the far east side of the Docks (Night), leading to a Run Down Alley. Upon entry, you will be confronted by Jess "Leashmaster" Varvel and another gang of slave hunters. Defeat these, and the quest is complete.

Note that some enemies may get stuck around a corner, and will require hunting down before the quest is marked as complete.

Rewards
Woodsman's Ire 1-handed axe, with 27 physical damage (51 per second), +32 health, +81 attack, +16% threat generation. Requires weapon-and-shield specialization, and 35 strength to wield.

Note: Gang-destruction quests, such as this one and Kind of Want create additional financial rewards from A Friend who is found in a back room of The Hanged Man after dark.