Creating a world populated by the Undead/Ghoulish

I'm currently working on a new world for a TTRPG style game using my own blend of rules and leveling systems (mainly my excuse to finally use the exploding dice mechanic AND skilltrees XD).

Setting: The world of HEAP! A city of chaos and uncertainty. The land is harsh, the weather even harsher, and the living conditions entirely impossible for any living creature. Luckily for its inhabitants, no one in HEAP is technically living. Everyone is undead, reanimated by some means within the bounds of this bizarred town. Only problem is: they can't leave. All those that have gone beyond The Burial Grounds are believed to have been deanimated and exorcised, never to be brought back. Is this the work of some mad necromancer's spell gone wrong? A cataclysmic event, a spiteful act of the gods? OR is there something even more cunning at play here? As an inhabitant of HEAP, you can play as a:

• Vampire - Skilled in persuasive manipulation and has enhanced senses
• Husker - Ghostly presence capable of possessing items and individuals
• Zombie - Shambling corpses that don't go down without a fight
• Spirit - Voices of the dead that possess immense control over magic
• Stitchbeast - Contructed monstruous beings with shocking capabilities
• Skeleton - Whoever they were, there isn't much that can stop them now
• Ghoul - Reanimated forms that have come back with a score to settle

The step I'm at currently is making the playable races in this world. I have a total of 7 right now and was hoping to expand based on any other undead mythical creatures or ghostly/haunting creatures that fit the theming of the world.