IguanaTweaks was a mod back in 1.6/1.7 days which made the game basically harder by simply modifiying vanilla mechanics or adding some new ones.
The mod was originally created by iguana_man and ported to 1.7 by Parker8283. In 2018 I've decided to take over and "reborn" the mod by rewriting it for 1.12. 2 years later the mod is undergoing another complete rewrite for 1.15+.
As 1.19 tons of stuff has been moved to Data Tags and JSON Configs. Check [1.19 and up] Tags and [1.19 and up] Json Configs.
REMOVED TEMPORARILY.
Bundled with the mod there's a datapack that changes a few aspects of the game:
The whole mod is split into Modules, each Module is split in highly configurable Features. Each Module / Feature can be disabled individually.