Preying on the Weak is a side quest in Dragon Age: Origins - Awakening. The Chantry of our Lady Redeemer's Chanter's Board in the City of Amaranthine is looking for assistance against groups of thugs who are terrorizing and extorting money from people outside the city gates.
Head south outside the city gates and deal with the four groups of thugs.
Once the thugs begin to move, the city guards can target them and will move to attack.
You can go up onto the battlements and cast an area of effect spell such as Blizzard on the group nearest the wall. Because they cannot path-find to the party, they will just mill around below until slain. The bystanders do not take friendly fire.
They can, however, bug if you approach them for the first time through the battlements. They won't move nor attempt to attack, and you'll be unable to attack them (either through area of effect spells or ranged attacks/spells). As such, you'll be trapped up in the battlements unable to leave, due to the fact that you can't open doors.
Unlike other Chanter's Board quests, there is no reward given by the Chanter. Instead, the experience reward for completing the quest will be received once all four groups of thugs have been killed. There is no need to return to the Chanter afterwards.