I found a server where the main thing is a fully custom Warzone that kicks in when you go past radius 50 from spawn. They say it is all coded from scratch as one plugin with procedural generation.

Once you cross in the sky locks to permanent midnight even if it is daytime somewhere else. The ground looks wrecked with craters obsidian spikes bone monuments with chains volcanic ash dead forests with cobwebs and magma veins splitting the earth. You also get soul colored particles and you hear creepy stuff like explosions whispers and Sculk Shrieker sounds. Sometimes red nametags show up then vanish.

Deaths matter too. If you die in the Warzone your spot gets a permanent glowing red stain and a Soul Echo that looks like a floating head. You can harvest it for souls but it tells everyone your coordinates.

Meteors can crash down with loot chests and some are Cursed. The Cursed ones give huge loot but you get Glowing for a long time and your coordinates keep getting broadcast so people will hunt you.

There is a roaming Blood Fog and if you step inside your screen goes almost fully black. If you have a lot of hearts and sprint an invisible Heart Seeker can follow you and it sounds like Warden breathing right behind you. The Warzone also has random lightning ground fog and when it rains orange embers fall from the sky.

It supports Java and Bedrock using Geyser.