Sculk

Sculk spreads from its source blocks across nearby terrain, and the Sculk Sensor, Catalyst and Shrieker blocks interact with it as they do in vanilla. A Shrieker needs a Sculk block underneath it before it can inflict Darkness on nearby players, and the mod adds a gamerule that stops Shriekers from making their sound when turned off. Catalysts can be set to spawn XP orbs above themselves instead of spreading Sculk, and they can detect game events such as walking or jumping, unless the entity is sneaking.

The mod works on client and server, so both sides need it. A set of gamerules controls the behavior: spreadMultipler, from 1 to 20, increases how fast Sculk Growths, Sensors and Shriekers spread, and another value controls how far Sculk Growths spread up and down. Sculk multithreading is switched on by default through the sculkThreading gamerule, which the author describes as the main performance setting, and it can be turned off if a server runs into low performance.

Sculk is released under the MIT License and is not open source. Its latest Fabric file is 1.0.13 for 1.18.1, published on 2022-01-23, and the mod has been available since 2021-12-25.