The depths of the Twin Rivers Oldwalls that dominate Haven.
Points of interest
Welcome, welcome to the depths. Loot the entrance area to find a Torn Piece of Parchment. Use the Amith Torchkey and Citrin Torchkey on the beacon, activating each of the floor plates that turn on (the northern doors opens with the Citrin, the western with the Amith).
Down the western corridor you'll find a couple of mercenaries repulsing the Bane. Help them and they'll explain that they were left for dead by Raetommon. You can let them live→ or kill them →.
Loot the bodies and remains. The corpse in the corner has another piece of parchment, creating the Blood Stained and Torn Pieces of Parchment. Use the Citren Torchkey on the beacon to activate the switch in the corridor.
Further down the corridor is a locked room. Open it with the switch to find Garrick.
Opposite his room is a plateau accessible through an extended bridge. You will find the Rho Torchkey here, on a Bronzeman corpse. Use it on the beacon.
Grab the charcoal rubbing on the wall (Lore 58) to unlock the second component of the Spire sigil.
In the beacon room, use the Citren on the upper left beacon, Rho on the central, and Amith on the upper right beacon to activate the floorplate. Continue through the door, picking up the Scroll Fragment from the body and Research: Magic Sigil from the cupboard.