All That Remains

All That Remains is a Main Plot quest in Dragon Age II during Act II revolving around the disappearance of Hawke's mother, Leandra.

Acquisition

 * Complete Prime Suspect and Offered and Lost

Walkthrough
You can optionally report Leandra's disappearance to Moira in the Gallows, though doing so has no lasting effect.

There are two ways to get access to the Dark Foundry:
 * If Gascard is alive, you can find him in Darktown. Tell him to perform the ritual. Perhaps reflecting the gravity of the situation, Fenris and Anders will let this one instance of blood magic pass without comment or consequence. Sebastian, however, still disapproves . If you turn down Gascard's offer to use blood magic, Sebastian approves of your decision and Merrill disaproves  . It is still possible to accept Gascard's offer after turning him down. After the instant transition to the Dark Foundry, Gascard will accompany your party through the area.
 * Certain dialogue choices may result in Gascard's execution by the Templars, rendering this option unavailable. If you cannot find Gascard in Darktown, speak to Moira in the Gallows and she will reveal that DuPuis was executed. Gamlen then becomes your only aid.


 * An alternative solution (and the only available path if Gascard was killed during Prime Suspect) is to meet Gamlen in Lowtown at night. Speak to the Urchin and either pay or intimidate him to obtain information. Then follow the blood trail to the Dark Foundry entrance.

Result
If Gascard DuPuis is with you in the Killer's Lair for the meeting with Quentin, there are three possible outcomes: Unlocks Following the Qun and The Captain's Condolences companion quests.
 * If Varric is in your party, he has a very interesting reaction. Youtube Spoiler
 * Without Varric you can persuade Gascard to turn away from his current path via a diplomacy (Diplomatic personality only) option. If successful he will fight alongside you in the battle with Quentin.
 * If Gascard feels disinclined to assist Hawke, he will join Quentin for the final battle.


 * The Gloves of the Overseer, Gloves of Enasalin, or Stonehammer Gauntlets are in a chest in the killer's lair, before the final encounter, depending on Hawke's class.


 * If you recruited Gascard in Darktown, and he survives, you can talk to him after in Darktown. Bringing Aveline or Fenris to interrogate him proves enlightening. If you let him go here,, if you kill him.