The Sanctuary is a tranquil area of the Shadow Lairs, that is entered from the Unknown Passage. It has been called "a calm in the storm" and "a fleeting dream, beyond the grasp of The Swarm". There are three points of interest: a Shadow Material, the Sanctuary Alchemy Machine, and an Echo Stone.
The Sanctuary Alchemy Machine, generating useful items for the terrors yet to come...
The Sanctuary Alchemy Machine is an alchemy station, akin to the Krogmo Alchemy Machine. It allows you to craft preset armor pieces, which can be made only at the machine. Crafting via the machine requires the materials and precursor for each item, in addition to the usual 5,000 crowns and 800 energy.
The final point of interest in the Sanctuary is a pillar of light that explains some of the backstory of the Shadow Lairs and the Swarm. The backstory presented depends on which Shadow Lair was just completed. Each party member acquires an Echo Stone artifact, that contains a permanent record of this backstory.