This is a server side fabric mod i made for my server because apparently there are no server side fabric mods for 1.21.1 out there that mirrors the bloodmoon plugin..

This mod only needs to be installed on the fabric serverside, no need for the client to have it. Every 7 days (i forgot to turn the day delay into a config option sry), a horde event happens that spawns zombies everywhere. Zombies will try not to spawn within 10 blocks of you, and will spawn within the radius you can set in /apocalypse setSpawnDistance.

You can also play around with some of the other settings in there like zombie spawn delay and zombie spawn amount per wave.

Access these command/config options by doing
/apocalypse <command>

(you can look through the available commands yourself im too lazy to paste them here right now)

So every day until the horde event day, what is supposed to happen is everyone gets a notification that a horde event is about to happen, but its not working and i will fix that someday.

There are also 2 extra features, every time a bonus zombie spawns during the horde event, cosmetic lightning will be summoned on the zombie.

In case you simply just skybase to avoid the zombies, there is one extra feature for that.

When you are above y=level 100 during the horde event, phantoms will start spawning, and don't think you can hide in a little sky bunker because the phantoms will explode your base when they crash into it (currently you are able to hide from them to avoid this by hiding in a little sky bunker but hopefully your players don't know that)

Also they will not explode in water or lava and will actually drain nearby water or lava so that they can explode on your wall in case you felt safe having a water defense on your skybase.