Cryptic Caverns DLC Concept, Plus new story arc.

First off, the final boss would be the Warden, or some kind of Diamond Monstrosity.

The levels would take place in the Dripstone Caves, Lush Caves and even the Deep Dark. I'm guessing that the end of the Orb of Dominance story will end with Echoing Void, so lets start a new story.

A rogue group of Illagers (which is saying a lot) has split off from the Arch Illager's former reign of terror. Enraged that such a power was given to an angry child, they seek a way of crumbling Villager life, all together. They venture deep underground, without any Villager slaves, only mindless golems. They mine for precious resources, decorating themselves in Emerald Armour and using the raw power of Diamonds, to create something that could level entire chunks; The Wither.

This could be the second chapter of this story. The first would be the discovery of The Wither from Chiseled Red Sandstone, in a Badlands Temple. They aim to travel back to the Nether, to gather the needed items for The Wither in the third chapter. Perhaps a Wildfire boss could appear and an Ancient pharaoh boss for the first chapter.