The Ender Infection

In this mod, by unlocking the Root End advancement, and going back to spawn in the overworld, you release awaken the Ender Core, the source of the infection's power. The core spawns on top of the player at spawn, as dorment upon starting the game. The infection spreads through a viscous goop/sludge substance that comes from the Core, and other Infecters. 

The infection starts slow, but quickly ramps up, currently there is no way to defeat it... Yet. The infection is heavily inspired by Minecraft Dungeons' Echoing Void DLC, thus some assets are borrowed from it.

It adds: Infected Cows, Zombies, Creepers, Spiders, Skeletons, Vindicator, Cod, Iron Golems, Foxes, and Blocks/Fluids, Corrupters, Summoners, Brutes (Walls), Leeches, Floating Eyes, Eye Portals, Goop Masses, and the like.