The Radiant Grudge

The Grudge awaits you...
Geckolib is required: https://www.curseforge.com/minecraft/mc-mods/geckolib

A vengeful entity has joined your journey, and it will haunt you and mess with your world, sometimes in smaller or larger ways.
The creature's name is the Grudge, it currently has 3 stages, and when you encounter it you'll get ambushed by it. However, it won't always kill you; instead, each encounter fills up your radiation meter by 1.

On the third encounter when all 3 dots light up, it will kill you.

You can deplete the radiation bar by searching Flowers of Remedy in lush biomes such as plains, forests and swamps. Using these flowers, 1 Bone and a Gunpowder, you can craft something called Remedy Dust. 1 Remedy Dust depletes 1 dot from the radiation bar.

Stages:

First Stage (9 minutes)

• The Grudge will lurk near you, but first it will release a greenish mist from the ground. When you go near the mist the Grudge will appear.

Second Stage (13 minutes)

• When switching stages, you can hear some ominous noises from the distance.
• The Grudge will continue to lurk near you, but nearby torches, lanterns, and wooden doors can get destroyed by it.
• Radiant Creepers start to appear that look like regular ones, but instead of exploding, they summon the Grudge.
• Sometimes it can drop Rotting Flesh blocks on you, which slow you down and drain your hunger. These will make noise so it will be more difficult to hear if a stalker mist is near. I really want to expand this event in the future...
• Bonus chests can start appearing in the world, but beware! There is a 50/50 chance that it is a legit chest, or the Grudge can hide inside it.

Third Stage

• Besides the mist ability, all previous ones from stage 2 will still be present.
• The previous mist event has been replaced with a mist stalker one. At night, a mist stalker can spawn on the surface, and it will start to slowly approach the player while breaking blocks in its path. The player needs to listen to the sound of the mist because it won't be visible, and if the mist gets too close then it speeds and begins to emit particles. Once it collides with the player the Grudge will spawn, but only if it's not already near. If it does exist then the mist will give the player Weakness effect and then it despawns.
• Poisonous spikes can come out of the ground under the player, which will then disappear.
• Weird sounds will be a bit more frequent.
• The Grudge can appear as a floating head, which will quickly charge at the player, raising the radiation bar by 1.
• It can also spawn with glowing green particles that fly towards the sky. In this state, the Grudge will slowly walk towards the player while destroying blocks, speeding up if the player gets too close. During this encounter, it will turn Grass Blocks into Coarse Dirt and plants into Dead Bushes. Sometimes poisonous spikes can appear at the same time as this event.

More Stages are planned!

Gamerules:

/gamerule grudgeActive true/false: Decides if the Grudge will be active or not.

/gamerule grudgeTimerOn true/false: Turn this to false if you don't want the Grudge to switch between stages.

/gamerule grudgeState 1/2/3: Decides what state the Grudge is currently in (Turn grudgeTimerOn to false first if you want to manually modify this!)

Future Plans:

More Stages
Instead of just appearing in generated chests, maybe the Grudge could hide inside your own chests.
Some kind of hallucination ability
A goal, or a way to fight back and defeat the Grudge by discovering and performing a ritual.

Note: I made this in the last minute for Halloween, so none of these are concrete plans yet!