Enter and speak to the three skeletons sitting at the table, this will begin the quest. If during The Vault of Braccus Rex the player smashes or consumes the soul jars inside the skeletons will be dead.
Once the player has done whatever they desire to the soul jars, return to the room with the skeletons, this'll finish the quest.
The following is optional.
Return to the skeletons and acquire the key off of Tamsyn's body, open the door.
Go into the inner area and go to the large source doorway at the back
If the player has finished Withermoore's Soul Jar up to the point where he is "dead" inside the cell you met him he will return when you interact with the lever next to the gate to open it.
If the player hasn't finished Withermoore's Soul Jar up to that point, cast Bless on it to open it.
Loot the room and acquire the Hands of the Tyrant from the right side coffin. This will progress Artifacts of the Tyrant.