Mystcraft

Mods
5,163,749 Downloads Last Updated: Apr 15, 2019 Game Version: 1.12.2

Lava World

A world with a lava sea, infinite plains, and glowstone crystal formations.

Nether Clone

Almost the Nether, but not quite... Closer inspection reveals the glowstone is elsewhere.

Tendrils

Wood, Netherrack, etc. This world seems composed entirely of tendrils.