Custom Buff Types

Custom Buff Types

Journey’s buff system is extensible. Third-party Fabric mods can register new buff types that integrate with Journey’s reward system, MoLang scripts, and commands.

For Mod Developers

This page is for Fabric mod developers who want to create custom buff types. If you’re a server administrator configuring buffs, see the Buff System guide instead.

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How It Works

Journey ships with four built-in buff types: attribute, potion, script, and shiny_chance. Mod developers can register additional types using Journey’s BuffTypeRegistry API.

Once registered, server admins configure custom buffs the same way as built-in ones — JSON files in config/journey/buffs/ using the new type name.

Example: If a mod registers a daycare_speed buff type, admins would create:

File: config/journey/buffs/daycare_boost.json

{
  "id": "daycare_boost",
  "type": "daycare_speed",
  "name": "Daycare Speed Boost",
  "description": "Pokemon eggs hatch faster in the daycare",
  "max_stacks": 3,
  "is_debuff": false,
  "hidden": false,
  "speed_multiplier": 1.5
}

The type field tells Journey which registered handler to use. The remaining fields depend on what the mod developer supports.

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For Server Admins

If you’ve installed a mod that adds custom buff types to Journey:

1. Check the mod’s documentation for the type name and available fields
2. Create a JSON file in config/journey/buffs/ using the custom type
3. Use it in rewards and MoLang scripts just like built-in buffs

Custom buffs work with all Journey systems:

• Task and levelable rewards via "type": "buff"
• MoLang functions: q.player.apply_buff(), q.player.has_buff(), q.player.remove_buff()
• Commands: /journey buff give, /journey buff remove
• Journey Client buff display

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For Mod Developers

To create a custom buff type, you need to:

1. Extend BuffDefinition — Define your buff’s configuration (loaded from JSON)
2. Extend BuffInstance — Define your buff’s runtime behavior (apply, tick, remove)
3. Register with BuffTypeRegistry — Map your type name to a factory that creates definitions from JSON
4. Register instance deserializer — So Journey can load your buff from saved data

The key classes are in the aster.amo.journey.buff package:

• BuffTypeRegistry — Register new buff types
• BuffRegistry — Register instance deserializers, apply buffs to players
• BuffDefinition — Base class for buff configuration
• BuffInstance — Base class for active buff behavior
• RemovalReason — Enum for why a buff was removed (EXPIRED, MANUAL, DEATH, SOURCE_REMOVED, REPLACED)

Refer to Journey’s built-in buff types as implementation examples. Registration should happen during your mod’s onInitialize() before Journey loads buff configs.