Zombies. I like the helplessness. "This thing happens, will happen, has happened, and you deal with it." I like them coming out at night. The dead rise when the moon comes up. (I think this brings a mechanic into the game of keeping track of time. When is it day and when is it night?)
Giants. Not DnD giants. I think they're lame. Lovecraftian giants. Colossi. Creatures who care not for us or our troubles. The world is theirs and we are the bugs that crawl the ruins. (I'm not sure what this means for the actual game. It doesn't change anything yet. It seems dickish, actually. As if the DM is saying "don't fuck with these things, hur dur, they'll kill you".)
Elves are cursed. All elves are cursed. They stay in the cursed woods. They are eleven feet tall and spindly like spiders. Their eyes are black, their hair is black. Their skin is paper white. They are a Tim Burton movie. (This means that people can only play half elves, and they have strange characteristics. Not sure what yet.) [Also, I think Drow are still a thing. I think they are elves born outside of the woods, or born on the moon, or something like that.]
Dwarves are alien. One day they just came up from the ground. They don't speak common. They don't like sunlight. They don't like weather. They like geometry. They worship something under the ground. No one has seen it. Not many dwarves have seen it. They stay out of Human endeavors and don't like trespassers. (This means that Dwarves have sunlight sensitivity, don't get common from the jump, and stick out like a sore thumb.)
Animism. The concept that everything is living and has a spirit. The most well known being is the Moon. It lives. It controls the undead. But mountains have spirits. Rocks have spirits. Dungeons have spirits, even if they are affluenced by their creator. (There are no gods. No pantheons. You worship a thing, like a family sword, or the king's throne, or the Moon. The people who worship the sun are blind and bat-shit-mad.)
The spirit world, or the Faraway. Everything has a spirit, and the spirit world is where all those spirits live. It's omnipotent and uncaring. Things don't like humans (living souls) very much. Monks, Warlocks, and Druids are the classes most intune with this plane. (There are no other planes. Just the world and the spirit world.)
Planes. There are none. Already said that. But all that shit that exists in Planescape and DnD is still real. They're just planets. They're up there in space and all but unreachable. They come to earth at times. Carceri stops by for dangerous prisoners, and Archeron comes by for the great march. (Space is something I like a lot and space travel/technology is something I like a lot and want prevalent in my game, but only for parties that want it.)
Animals. They're special. A lot of them are intelligent and are intune with the spirit world. Careful. All black cats are assassins for the Black Dot. (Fairy tale logic. You can't lie to a dog. Flies are said to cure disease. Rats keep secrets. Snakes are books.)
Playable races: Human (5e, variant or not). Everything else is uncommon. A few of the more common of the uncommon (ones that don't need a special story): goblins, ratfolk, tieflings, dragonborn, half-elf, drow, the android things. Goblins come from the everwood, ratfolk come from the sewers, tieflings are bastard children, dragonborn are the same, half-elves are the same, and drow are just elves born outside of the cursed wood. The android things (forgot the name) are around because of technology.
Health potions are syringes. Guns are wands and have charges.
The biggest one, which will dictate my entire world, is that ADVENTURING IS A SPORT. It's televised. It's watched by everyone. It's the highest paying job with the highest risk. Parties have names and can become famous. Dungeons are bought by people and used to hold events where people can dive and die for a chance at riches.
That's it for now. I'm just trying to sort things out. A part of me thinks it's not worth it. Maybe just make the dungeons and the world will come from it? idk.