Spatial Difficulty.

Solve three birds with one stone! Give the world an inherent choice of risk and reward, give players a reason to stick together, and prevent new players from joining and immediately dying to a skeleton with an enchanted bow.

Summary

This mod repurposes the vanilla 'local difficulty' mechanic to be determined by distance from spawn instead of time in a chunk (capped at the same values as vanilla). The mechanic is otherwise identical--causing mobs to gain more armor and weapons, have more enchantments, and special versions (i.e. potion spiders).

Config

The rate of difficulty growth can be edited in config, and the center will always be worldspawn.

Compatibility

There should be minimal performance impact. Will have incompatibilities with any mod that changes how local difficulty works, but that should be basically none of them. Should work entirely serverside, but if not on client the debug screen will show the incorrect difficulty.