Underground Labyrinths

Because we need a cave update I think that stumbling upon an underground labyrinth would be cool!

I envision it to play similarly to other rogue like dungeon crawler games with random room generation and layouts. It could look similar to the stronghold in appearance but would be constructed out of a new "Labyrinth brick" block (with stairs and slabs too). These blocks would be indestructible until the player reaches the end of the dungeon and mines out the "Labyrinth Core", only then can they be mined by the player. This forces the player to traverse through the dungeon in order to obtain the loot instead of just mining through it. It could also have new mob types that the labyrinth would be full of, and potentially even a boss at the end of it.

Ideally, these would be large structures that would add more adventure to the game while simultaneously making mining underground more interesting.