Welcome to The Dark Under! Living underground is nice, there isn't any of that pesky light. Though getting things like wood and food can be a bit of problem.

Can you scrape out a living? While you are completely accustomed to cave living you still need food and wood for tools. Growing crops can be a challenge when the torch light is a bit too much for you. And sure you can go visit the villagers and even get wood but best do that at night.

There's one other problem as much as zombies like human flesh... they LOVE deep dwellers flesh (that's you) . So, you know, the zombies are faster, more prevalent and can see you from further away. On rare occasion they might even bring zombie lord along. It's tougher but otherwise "harmless". So, Making those night romps and general caving to get resources a little dangerous.

Notes on gameplay (as of 1.1)

zombies are faster and far more plentiful. they will become aggressive from further away. The drop bones in addition to normal drops.

zombie lords also drop an emerald but otherwise they drop zombie loot.

you take 1 damage a second if it gets too bright (say with in 2 blocks of a normal torch, or lava or fire) . this is raw damage not fire or fire damage.

you take 3 damage a second if it gets really bright (pretty much only from sunlight). this is raw damage not fire or fire damage.

you have perma night vision (no particles, renews ever 6 seconds)

you can eat bones and bone meal. (yes really)

you have increased lung capacity (you run out of air 1/2 the normal speed).

The light level in the nether and the end is low enough by default you wont get hurt out in the open. Same is true for the surface as long as the sun is down.

There are recipes in game to make leather from flesh, health potions with out a brewstand, cobble stone from dirt and bone. sticks from bones and soul sand and soil for low light torches.

Your start the game underground with a chest of basics a soul fire camp and a crafting table.

notes in general

you could combine this with hollow earth for a true "creature of the night" gameplay experience. https://www.curseforge.com/minecraft-bedrock/addons/hollow-earth . starting up a new game with both ~should~ put you below the crust. both addons try adjusting your starting position so... yeah. not entirely sure which wins. either way good times.

I might add more to this. maybe a loot table for the zombie lord or other "special" creatures of the night if this proves popular or there is general interest or ideas people would like to see.