The place they arrive at is in much better repair than the ramshackle town Thresh had been trying to build. It is, in fact, fairly recognisable to Avedra, if she's ever been to the capital, Helia.
They're in a garden, and while normally one would want to add caveats about how gardens are not typically made with (un)dead plants, this somehow actually works. The colours are dark greens and blues and purples and the occasional red, but it is artfully decorated nevertheless, a gloomy aesthetic that is enhanced rather than diminished by the fact that most of the plants are not alive. There is a pond, its waters dark and hard to see into, with the kind of occasional movement that suggests the existence of (probably undead) fish. In the middle of the pond is a tiny isle with a single dead tree planted on it, pulsating ruby veins decorating its trunk and faintly illuminating the surroundings. It's small, probably private, and a little emerald cobblestone walkway leads to the ruins of the palace.
And they are ruins, the walls are cracked and broken, vines crawl along the whole structure, various turrets are held up only by the Black Mist itself. Yet, it seems much more purposeful than the ruins she's seen so far. The village Thresh had been building was trying to carve out a semblance of normalcy out of the chaos; this place is harmonising with the chaos, using the dark magicks that haunt this place to enhance it rather than tear it down. She may observe that actually the roofs of the palace are mostly intact, and the bits that aren't intact seem to have been turned into localised art installations, with magically placed debris forming abstract floating sculptures and evil-looking vines linking them together into something cohesive.
If there is a way to draw out beauty and prosperity out of death and decay, this is it.