The Upside Down World:

When you create a world, you will be automatically be in the Upside down world, idk how to make a dimension, so i just changed the overworld.

Update: The particles are now minimal, and when you have night vision, The world will turn into a red foggy.

MOBS:

Demobat:

Health: 20

Damage: 6

Speed: normal 

This mob spawns in groups and they can spawn everywhere in the world.

Demodog:

Health: 23

Damage: 6

Speed: normal 

Update: the new demodog has a new texture and new behaviour, this mob now spawn in groups.

Demogorgon:

Health: 67

Damage: 8

The Demogorgon can run,but you can outrun him so that you can escape him because there are alot in the world.The Demogorgon can only see 20 radius far.

Mind Flayer: 

health: 463

damage: 21 

effect: blindness 

effect_duration: 10 

speed: 0.23 

this mob will spawn everywhere, but this mob will be hard to find 

Items

Night Light:

This Item can give you a night vision effect so that you can see clearly because the world is so dark.

This item is craftable, to activate it, you need to put it in your off hand.

Pipe And Baseball Bat:

This two weapon can help you defend yourself in the world.This two weapon is craftable

There are hazmat suits in this addon.but i forgot to screenshot those.

Portal:

For now, the portal doesnt do anything,maybe in the next update i will give it some functionality.

Video:

V2.1 Trailer

this is just beta, so you might encounter some bugs or glitches in this addon