World Blender - Fabric

Its World Blender dimension is built from a single biome's worth of features and structures, with surfaces, caves and terrain shoved together from many sources. Modded features and structures are added to the dimension too, and some of them normally spawn only in their own biomes, so the mod works around that. Config options on the mod's own features decide where their output appears, so checking those options first is the usual way to control spawning. Requires Cloth API and Fabric API.

Surfaces follow a fixed layout: a Nether-style path runs through the dimension as the main walkway, and End-style surfaces sit on the sides. Massive webs, tree-filled areas and grass structures interrupt that path, and animals spawn less often under dense tree and plant cover, which can be adjusted by blacklisting plant features. Players can add ores from other mods, and biomes imported from mods bring their own mob spawn entries. The mod is published for 1.16.5 – 1.17.1 on Fabric, and Fabric's latest file targets 1.17.1.

Removing the mod and reinstalling it restores the dimension, but the Nether and End dimensions can go missing after a Mojang bug, so a backup copy of the world is recommended before adding it to an existing one. On servers the dimension JSON is created only when a world is generated, so a fresh world must be made with the mod installed and the server restarted afterwards.