The Strange Mausoleum is a sewer location under Lanilor Lane in Aleroth that is accessible from the ground floor of Taurus' House and the private chambers of Luxurius' Mansion during the events of Divinity II: Flames of Vengeance.
The sewer water is poisonous, and the area is infested with level 39 skeletons and rotten undead. Depending on where you enter from, you'll either begin in the southwest corridor (Taurus' House entrance) or south-central corridor (Private Chambers entrance). Regardless, the two corridors meet at a three-way fork (east-west-south), where you'll find a Red Ore vein in the water.
Go a short distance east from here to the next fork (east-west-north). Ignore the Iron Chest further to the east for now, as it is locked and requires a key. Proceed north to where the passage turns west. There is another Red Ore vein in the water here, along with the Iron Key needed to unlock the aforementioned chest on a pile of rubble in the far northeast corner. Go back and loot the Iron Chest after picking up the key, then press ahead until you reach a four-way intersection.
To the west you'll find lockpickable chest containing random loot and two Moonshine plants. To the north there is an unlocked chest (also contains random loot), a Red Ore vein, and a Moonshine plant. In the large room to the west is yet another Red Ore vein and three more Moonshine plants around the parameter.
If you took Tom's Severed Finger for the quest Beauty And The Beast and have entered the mausoleum via Luxurius' private chambers there is no need to solve the statue puzzle. You can slaughter more undead in the large room to the west, then exit the area via Taurus' House or by returning to the private chambers.
If you've embarked on the quest Beauty And The Beast and allowed Tom to keep his finger, you've entered the mausoleum via Taurus' House. You'll need to solve the statue puzzle to acquire the Private Chambers Key and find Luxurius.
The rooms to the north and east each contain two statues with a rune in front of them. Note the color of each statue and its rune.
To obtain the key you simply need to interact with the statues in the western room and replicate what you observe in the other rooms. From north to south:
This causes a chest to magically appear in the corridor containing the key.
- Chest – unlocked, contains random loot
- Chest – unlocked, spawns after completing statue puzzle, contains Private Chambers Key
- Chest – locked, lockpickable, contains random loot
- Iron Chest – locked, key required, contains random loot
- Iron Key – unlocks Iron Chest
- Moonshine Plant – ×6
- Red Ore Vein – ×4