Blade Grave Oldwalls - Central is a location in Tyranny.
Points of interest
Welcome to the Oldwalls. The first room has one Scourge and several Wisps, with more arriving when you approach the small mirror on the eastern wall. After they're dead, use the Garn Torchkey on the floating rune.
Enter the hall. Fight more Magebane, then collect the charcoal rubbing from the symbol on the other side of the hallways.
Continue down the hall. Mind the trap (44 Subterfuge). Approaching the center will reveal the body of the First Regent and the trapped Havoc. To progress further, you need to gather and install keystones.
The first is the Humming Keystone found on the Scribe's body. Use it on the nearby receptacle to power up the stone button near the entrance to the Havoc chamber. Activate it to access the upper floor.
Enter the upper left chamber. Cross the bridge, pick up the Stone of Elucidation. Use a piece of rubble found nearby to weight the altar down to return.
On the right-hand side, enter the corridor (mind the trap). Use the stone on the wall to toggle the doors and open the beacon room to the south, with a Malice and two Scourges inside. Fight through them. Use the red torchkey to activate the wall switch and use it. Open the locker to acquire the Cold Keystone.
The Havoc is released by acquiring all of the keystones and installing them in a clockwise manner.