Inside the BDC there is a new portal called Deeper Catacombs. This is not the same deeper catacombs as the one for the olthoi weapons quest.

The new portal looks very unstable. By the description of the portal, it seems you need a quest flag to enter it. As of now no one has figured out how to enter.

The portal is in a small room very close to the entrance - its directly connected to the first room. The portal is guarded by the new virindi/shadow altered Olthoi, and scattered around it are corpses of nan-jou from the Tanada house of water.