The Archdemon (Mosaic)

The Archdemon is a mosaic in Dragon Age: Inquisition. "Pieces of an old Tevinter mosaic are scattered across the Western Approach. If recovered, they could be reassembled."

Acquisition
Triggers when any mosaic piece from this collection is found.

Walkthrough
The 12 pieces are found in the Western Approach in the following locations: Piece number unconfirmed:
 * 1 piece in Sand Rock Mine near the Red Lyrium vein (Piece 1)
 * 1 piece Outside of Still Ruins (Piece 2)
 * 1 piece in the Lost Wash Creek Cave (Oasis Cave) near "Lost Idol" Landmark (Piece 3)
 * 1 piece in The Thing in the Dark Cave, in Death Drink Springs, requires Crossing the Sulphur Pits operation (Piece 4)
 * 2 pieces in the cave which becomes accessible after the Abyssal High Dragon fight. (Piece 5, 6, likely). If the entrance is still blocked after the dragon is killed, a Grappling Chain can be used to break the rock.
 * 1 piece in Cave at the end of On the Chantry Trail (Piece 7)
 * 1 piece below the Hidden Stairway (Piece 8)
 * (Piece 9)
 * 1 piece NE of Gates of Andoral (past Coracavus) (Piece 10)
 * (Piece 11)
 * 1 piece under Griffon Wing Keep in the Old Well (Piece 12)
 * 1 piece In Echoback Fort (past Coracavus)
 * 1 piece in the Astrarium Cave

Rewards

 * 50 XP for each mosaic piece
 * 200 Influence for collecting all 12 pieces

Results
Recovering every piece of the mosaic and letting Gatsi translate it unlocks Codex entry: The Mason's Tales: The Archdemon.

The recovered mosaic can be seen on left side of Skyhold main hall, closest to Gatsi.

Bugs
After collecting all 12 pieces, one piece can be missing from the mosaic displayed on the wall at Skyhold. You'll still be able to talk to Gatsi to receive the codex entry as if the mosaic is complete however. (PS4) (Xbox One)