Equivalent Exchange 3
To summarize: this mod allows you to transmute tons of materials into other materials. It adds a lot of what is classified by many as "endgame content", to make you feel more godlike in your sandbox world. If this offends your Minecrafting sensibilities, this may not be the mod for you.
These items are psychotically expensive, so before you bash them, try acquiring the items legitimately. You'll find it's not exactly a cakewalk.
This (and other) pages on CurseForge are a work in progress as I port and reformat documentation over from MinecraftForums. Please be patient.