Void Pressure

A single Pressure value is kept for the world, and its level changes over time and when mobs die, so mob death adds tension. Configurable events react when Pressure crosses set thresholds, and the mod itself does not dictate what happens. Each trigger can fire once or repeat at set intervals, and some pressure can optionally decay over time. The author describes the system as a base for modpack makers rather than a finished gameplay loop, with the core systems stable and further features and extensions planned.

Void Pressure is built for modpacks and was inspired by a Skyblock modpack in which the world type responds to player actions. Rules select mobs by tags and categories, so an event can change only specific entities, such as making them more numerous or altering their behavior. Mob kill increases are capped per minute to limit farming abuse. The optional Pressure Altar lets players actively lower the value, and the Pressure state persists permanently in the world. Open the GUI with Shift + V to inspect it.

The mod is published for NeoForge 1.21.1 only, as a beta with version 0.6.0. Every player and the server need a copy of the mod. It is released under the Creative Commons Attribution Non Commercial 4.0 license and is not open source, although source code, an issue tracker and a wiki are public.