Find a small hill in the Overworld. You need to use a Magic Stone — crafted from diamonds, bottles o' enchanting, and three emeralds — to activate the bedrock portal hidden inside the hill, which will take you to a mysterious Underground world.
Version 0.1 is very rudimentary, yet it already features two new biomes, a full set of new equipment, several new materials, four new generated structures, and a boss worthy of your challenge — Undyne — waiting for you to discover.
Although there are some limitations, I have decided to continue developing on MCreator. I will combine it with IntelliJ IDEA and try my best to complete the 1.0 official release (waterfall area complete and snowy plains test).
https://mcreator.net/modification/122859/undertale-wrold