Justice (quest)

Acquisition
In the beginning of Act III, you must complete the Check on Anders quest. You must then travel to Ander's Clinic with Anders as your companion to get this quest.

Walkthrough
Help Anders collect two potion ingredients. First is in the sewers of Darktown called Sela Petrae. There's about five deposits you need to collect. You'll also encounter lyrium smugglers along with a lot of traps and some apostates. The second ingredient is a rock called Drakestone which can be found in the Bone Pit mines. Like in the sewers, you must find five deposits of Drakestone. You will also find a few traps along with corrupted and poisonous spiders. Note there is also a Monstrous Spider waiting for you in the larger area of the mine. Keep your eyes out for a Warden's Oath amulet and a Griffon-Feather Belt in the Bone Pit mines. Afterwards head back to Anders' Clinic, where Anders will want to speak to you privately. He will ask you to go to the Chantry to distract the Grand Cleric. At this point you have an option to decline to help him or not. Go to the Grand Cleric and talk to her. You have the options of asking for the Maker's blessing, to talk about mages and to say goodbye. If you choose the mages topic after the Grand Cleric spouts her wisdom you have the option of "The mages need your help." "Why not?" and "So you support the templars?" The Grand Cleric will the talk about feeling for both sides and hope for balance. At this point Anders will appear and you can leave. Once again, head back to Anders clinic to speak to him once more.

Result
Anders gains a new outfit(Renegade's coat), a black verson of his original outfit. During the finale of Act 3, during a discussion between Orsino and Meredith, Anders will step forward and will use the ingredients you helped him gather to blow up the Chantry, killing everyone inside. After you choose to support the Mages or Templars, you get the choice to let Anders leave, keep him in your party, or kill him. (Note that this will occur anyway, regardless if you take this quest, it will just happen without you being complicit.)