A library mod for adding End and Nether biomes or structures, and for creating new biome ambience!

Also unifies different older mods' End and Nether biome generators under one system, fixes respawn dimension logic and other bugs, and offers new settings for the End and Nether.

If you're a modpack developer wanting to add Nether API to a modpack distributed outside of CurseForge or Modrinth, use File Director to avoid reuploading Nether API's files.

API Features:

Ability to add custom biome ambience!

This is applicable to any biome, not just End or Nether biomes.
Can have passive ambient sounds (can also be set with BiomeAmbienceEvent).
Can have a custom darkness ambient sound (can also be set with BiomeAmbienceEvent).
Can spawn passive particles (can also be set with BiomeAmbienceEvent).
Can have a custom lava color (idea provided by Mellohi).

Ability to add custom End and Nether biomes!

Can have a custom biome generation weight (can be set with NetherAPIRegistryEvent).
Can have a custom fog color (can also be set with NetherAPIFogColorEvent).
Can have a custom music type.
Can have a custom surface builder, and a custom chunk populator.
Can have custom cave carving conditions.
Can have custom Chorus Plant, End City, and Small End Island generation conditions (End biomes only).
Can have multiple weighted sub-biomes and edge-biomes.

Ability to add custom End and Nether structures!

Can generate between chunks (like Nether Fortresses).
Can have custom entity spawning properties (like Nether Fortresses).
Can have custom generation conditions.
All registered structures automatically work with the /locate command.
All registered structures automatically check for other structures when generating, so they won't intersect.

New EnumPlantTypes!

These are applied automatically by Nether API to various modded End and Nether plants and soil blocks, to let them respect other mods' "End Stone"-like or "Netherrack"-like soil blocks. This allows for new inter-compatibility between any plants and soils from different mods that use them!
PlantUtils.END_PLANT_TYPE: This PlantType is for any plants that can be planted on "End Stone"-like blocks. At runtime this is automatically applied to Vanilla's Chorus Plants.
PlantUtils.NETHER_PLANT_TYPE: This PlantType is for any plants that can be planted on both "Netherrack"-like blocks and "Soul Sand"-like blocks.
PlantUtils.NETHERRACK_PLANT_TYPE: This PlantType is for any plants that can be planted on "Netherrack"-like blocks.
PlantUtils.SOUL_SAND_PLANT_TYPE: This PlantType is for any plants that can be planted on "Soul Sand"-like blocks. This field just set to Forge's EnumPlantType.Nether, since they serve the same purpose.

Mod Features:

Features:

Allows end biome mods to work together by unifying end biome generation code!

Allows nether biome mods to work together by unifying nether biome generation code!

Allows users to define a default "player spawn dimension" through new config settings!

Automatically enables Forge's cascading world gen fix during End & Nether generation!

Caves can now generate in the End's outer islands!

Nether caves can now carve through biome top/filler blocks and soul sand (instead of only netherrack)!

New config setting to disable the first Ender Dragon spawn. When this setting is active: an End Gateway will generate, the Ender Dragon can still be summoned using End Crystals, and the dragon egg still appears after the Ender Dragon's first death.

The Nether can now be 256 blocks tall!

This feature is disabled by default.
This feature should only be enabled for new worlds (or old worlds if you reset the Nether first).
For many mods that generate their own nether features, you'll have to adjust their configs to account for the new height. Currently all mods that Nether API adds its own support for (and do not require manual config editing) are as follows (it's also assumed that any mods using Nether API as a dependency have automatic support for this feature):
- BetterNether, BetterNether: RotN Edition, and BetterNether Continuation.
- Biomes O' Plenty.
- Journey Into The Light.
- Natura.
- Nethercraft Classic.
- NetherEx.

Fixes:

Fix "initial spawn position" bugs for many dimensions (like positioning players in lava or well above the ground).

Fix MC-10369 (Certain particles do not get spawned):

Baby animal spawning particles.
Ender dragon block destruction particles.
Entity teleportation particles.
Eye of ender placement particles.
Fluid mixing effect particles.
Iron golem creation particles.
Redstone torch burnout particles.
Snow golem creation particles.
Wither creation particles.

Fix MC-31681 (Fog and clouds darken when you're under any blocks).

Perform initial spawn chunk load for the "player spawn dimension" instead of the overworld, and generate spawn positions for all respawn dimensions.

The Ender Dragon can now longer destroy blocks with a blast resistance of obsidian (enchanting tables, ender chests, etc.). Also prevent the Ender Dragon from being able to destroy torches (as they're a part of the exit portal).

Respawning now accounts for all of Forge's per-dimension bed spawn points instead of only the current dimension. This change alone fixes some mods (like aether beds not working if you die outside the aether), and greatly simplifies the respawn logic needed by mod developers wanting to add a dimensional respawn point.

Special Mod Compatibility:

BetterNether

All three versions are supported (BetterNether, BetterNether: RotN Edition, and BetterNether Continuation).
BetterNether uses a pseduo-biome generation system, this mod disables that and gives it real biomes.
Heavily improve performance when generating features (by not causing block updates). This also fixes several cascading world generation issues.
New config setting that allows eye vines to generate in Biomes O' Plenty's "Visceral Heap" biome.

Biomes O' Plenty

Add config option to allow the fluids from Biomes O' Plenty that already generate in the Nether (Blood and Honey) to not vaporize in the Nether when placed through a bucket.
Add config option to toggle world-type dependency for BOP's nether biomes, allowing them to spawn even when the world-type isn't set to "Biomes O' Plenty".
Fix BOP dynamic trees addon creating dirt in the nether.
Fix BOP nether bramble cascading world generation issues.
Fix BOP nether hive cascading world generation issues.
Fix BOP nether lava cascading world generation issues, caused by that mod copying Vanilla's code but not copying Forge's fix for it (see MC-117810).
Prevent BOP from hiding its cascading world generation issues from the logger (lol).
Prevent BOP from removing End and Nether fog.

Journey Into The Light

JITL uses a pseduo-biome generation system, this mod disables that and gives it real biomes.
Fix all of JITL's Nether cascading world generation bugs.
Fix certain structures using bad entity ids for spawners (caused lots of log spam and broken spawners).
Improve performance when generating JITL's Nether features (by not causing block updates).
JITL's Nether entities now spawn only in JITL's Nether biomes instead of Vanilla's Hell biome (any can be reverted via GroovyScript):
- Hell Cow: Now only spawns in the Blood Forest & Blood Forest Edge biomes.
- Hell Serpant: Now only spawns in the Heat Sands biome.
- Hell Turtle: Now only spawns in the Heat Sands biome.
- Inferno Blaze: Now only spawns in the Blood Forest biome.
- Mini Ghast: Now only spawns in the Blood Forest biome.
- Reaper: Now only spawns in the Earthen Seep biome.
- Witherspine: Now only spawns in the Earthen Seep biome.

Natura

Only generate Natura's Nether features in Vanilla's Hell biome, as they usually are very out of place in modded ones. Other biomes can be whitelisted via GroovyScript.

Nethercraft Classic

Add new "Glowing Grove" biome that Nethercraft now adds all of its features into.
Fix all of Nethercraft's cascading world generation issues.
Fix Nethercraft's bad entity network registries (also fixes weird projectile behavior).
More of Nethercraft's entities are now fireproof.
Nethercraft's Dark Zombies are now summoned instead of normal zombies during SummonAidEvent while in the nether
Nethercraft's Slime Eggs can no longer spawn entities on the client.

NetherEx

Add functionality for NetherEx's previously unused config values for soul sand and gravel generation.
Fix bad structure size check, no longer causes cascading world gen when checking structure placement.

Stygian End: Biome Expansion

All three versions are supported (Stygian End: Biome Expansion, Stygian End: Unoffical, and Stygian End Continuation).
Chorus Plants no longer generate in Stygian End's biomes (each can be toggled via configs).
End Cities no longer generate in Stygian End's biomes (each can be toggled via configs).
Fix all of Stygian End's canopy cascading world generation issues (done by drastically changing how the trees generate, can be reverted via configs).
Fix all of Stygian End's volcano cascading world generation issues.
Stygian End's acidic plains biome features now generate only on end obsidian.