The Necropolis of Zuthmadyr

QR notes
The Necropolis is free to use for any QR - you can basically have any level of quest inside, the only limit is you can't kill the big-bad lich in charge. He has fun rearranging the rooms, so there's basically no set layout, it can be whatever you want, and the tombs/enemies can be from any plane/source, but are almost always undead/spook

Lore Notes
It's a giant necropolis assembled by this lich from across the planes, containing chunks of hundreds or thousands of graveyards, crypts, catacombs, and dungeons. He goals are unknown, but it was definitely his plan to bring it under Osteria... for whatever reason

There are a group of two revenant twins. They are out killing undead and could be an interesting random encounter/random help if the party is dying due to bad rolls. They do not like people who disrespect their legacy and will seek revenge against those who do so.. One of them has a magic greatsword, and the other has a dagger sized dragon tooth. But they will happily use fists if that would be simpler for those running them.

There is a large room filled with undead that has been hallowed dead cannot be raised in the room and undead will have difficulty entering it. Powerful enough undead could potentially unhallow it in the future. The room seems to be a massive throne room filled with corpses. Holes are in the ceiling, where bodies are dropped on occasion.

An undead adult red dragon currently is roaming around the Necropolis. It is seemingly puppeted by large green vines. It is intelligent but is not a lich or magic user. It will very weave back together unless its wooden heart is destroyed (the heart is very small and can be found with a dc 20 invest check). The entire body is magical with conjuration magic. It will also be destroyed permanently if it is both at 0 hp and a Blight spell has been cast on it at some point.