Inverse Blocks is a mod that adds something called Inverse Matter:
There are currently four amulets:
Amulets require being charged in the Charging Pedestal.
The Infusion Pedestal must be used to craft some materials and/or tools. It can be also used for transmutation of some vanilla items into there inverses(Rotten Flesh -> Leather, Grass -> Mycelium, ...).
The mod also adds powerful tools like the Inverted Diamond Pickaxe that can mine blocks in a 3x3 area. It can be made via Infusion crafting and the Inverted Diamond Axe which will auto-smelt any smeltable harvestable block.
You can find more information on the pages tab.
You can use this mod in your modpack.
The mod has an in-game guide, but I recommend using JEI with this mod.
This mod is still in development.
No files available for download.