Veil of the Once-Queen

Deep in the forest is the citadel of Tanibel, once the capital of Martoi. Although their time has passed, they have found a way to cling to the world by straddling the veil between life and death.

In my home campaign, the three Lords of Tanibel have ridden out and poisoned entire watersheds with the black draught, leading to the terrible undoing of society hinted at in the Unmended Way.

Even if you don't go quite so apocalyptic and campaign-defining, Tanibel is still easy to slot into any forested region of your campaign world. Treat the Martoi like a fey court with a particular obsession with treachery.

The gray proctors are probably my favorite part of this one, if players haven't figured out what's going on with the veil by the time they get to the gates, I think there's potential for a truly horrible realization.