The mod add 3 new dimensions, 2 new sets, the end/best_set:

and the cosmo_set:

that are way more powerful than the vanilla sets, 2 new bosses that are "The King" and the "Cosmo King", "The king" can kill a warden and survive with a bunch of hearts, if you kill him you can have the "Staff of the King" that can spam special projectiles that you have to craft ; the Cosmo King is a boss that have a lot of life, he can one shot you if you don't have a part of the cosmo set and if you kill him, he drop you the cosmo_sword