spork
spork is a Minecraft mod for spork.homes. It rebuilds the underground as a 640-block-tall world with its own biomes, replaces enchanting with an alchemy of sixteen virtues, and adds mobs, materials and light that vanilla does not have.
Where to start
The world is stretched vertically. Sea level sits at y444 and the ground runs down to y0, with two cave bands under the ordinary stone. Every underground region is a biome with its own rock, water and inhabitants.
Alchemy replaces the enchanting table. A virtue is fixed into a body by beam and vessel, and what the virtue then does depends on what the body is.
Reading this wiki
Each page opens with what a player needs in order to use the thing. Mechanism follows, for contributors. A badge under the title marks anything not finished: partial, placeholder or known-bug.
Developer tooling has its own section and describes the probes, benches and build gates rather than anything a player meets.