Isekai API

Create a custom world shape without building an entire world-generation system from scratch.

Isekai API is for datapack authors, mod developers, and pack makers. Combine terrain shapes, biome rules, and placement tools to build floating islands, shells, mountain ranges, layered worlds, or other layouts.

Shape the world

• Combine terrain primitives and choose where biomes appear.
• Set surface materials, sky, fog, and water colors.
• Place features and set-pieces such as pools, trees, and structures.
• Adapt supported ores, mobs, and structures to new heights or to an island’s own surface.

These tools can be used for a new dimension or an overworld replacement. The library supplies the building blocks, rather than a finished themed world.

Try an example

Start with the floating-island datapack, then adjust its terrain rules. The Datapack Reference and example collection cover the available JSON options.

Java integrations use the public Isekai API. See the dependency and compatibility guide, and match examples to your installed release.

Test world-generation changes in a new world first. Unrelated to the Isekai Adventure modpack.

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Questions, ideas, bugs: open an issue.

MIT License. Free to use in modpacks.

Source: https://github.com/KURONAMI333/isekai-api

Bugs and questions: comment on the CurseForge page or DM @kuronami333 on X.