Let mobs become bigger or smaller.
It provides Potion of Magnification and Potion of Shrinkage.
When the player becomes bigger, the player will move faster. Attack damage will increase. Resistance increase. The player can break multiple blocks at the same time. But the player will consume more food.
When the player becomes smaller, the player will take more damage. But the player will not possibly be noticed by hostile mobs.
You may see scalable slimes in swampland or caves. These slimes can change its scale randomly. You can get Magnifying Essence or Shrink essence by killing it. Then you can brew potions using the essence.
Use magnifying essence to brew an awkward potion, you will get the potion of magnification I. Give it another essence, you will get level 2 potion. Then level 3 potion. The same applies to the potion of shrinkage.
This mod is based on Fabric API (not forge).
How to install fabric: https://fabricmc.net/wiki/tutorial:install_with_minecraft_launcher
Don't forget to add this: https://www.curseforge.com/minecraft/mc-mods/fabric-api