FIW Bosses

A data-driven custom boss framework for NeoForge 1.21.1, Fabric 1.21.11, and Fabric 1.20.1 — inspired by MythicMobs, built from scratch.

Define fully custom multi-phase bosses entirely through JSON files. No coding, no server restarts — drop a config, reload, and your boss is live.

Why FIW Bosses?

Neither Fabric nor NeoForge has a good lightweight boss framework. MythicMobs is Bukkit/Spigot only. FIW Bosses fills that gap — server-side only, zero client installation required, fully JSON-driven so anyone can create bosses without touching code.

Supported Loaders

Loader Minecraft Status NeoForge 1.21.1 Active — primary development target Fabric 1.21.11 Active — current Fabric target Fabric 1.20.1 Legacy — may still receive occasional updates, but not guaranteed

All three ports share the same JSON schema, same 42 abilities, same minion system, same commands. A boss config written for one works on every other — drop the same file into NeoForge or either Fabric branch and it behaves identically.

Features

• JSON-driven bosses — create any boss without writing a single line of code
• Multi-phase system — HP thresholds trigger phase transitions with new abilities, speeds, equipment, sounds, and particle effects
• 42 configurable abilities — melee, ranged, mobility, AoE, crowd-control, utility, and ultimates
• Custom minion system — define custom minions via JSON with their own stats, skins, equipment, abilities, loot, and AI modes (normal, follow boss, static) — or use vanilla mobs with stat overrides
• Pre-fight activation — boss starts passive and immortal; right-click to trigger dialogue and start the fight
• Pre-death dialogue — boss held at 1 HP on the lethal hit, speaks final words, then dies
• Custom skins — use any player's skin or load a local PNG file (bosses and minions)
• Custom equipment — full item and NBT support per slot, swappable per phase
• Dynamic aggro — aggro switching, revenge targeting, multiplayer-friendly
• Strafing AI — bosses circle and strafe at close range
• Custom loot tables — per-item drop chances with full NBT support (bosses and minions)
• Hot reload — reload all boss and minion configs without restarting the server
• Phase persistence — boss phase survives server restarts
• Server-side only — clients don't need to install anything

Quick Start

1. Drop the correct JAR into your mods folder (NeoForge, Fabric 1.21.11, or Fabric 1.20.1 variant)
2. Start the server — the config folders generate automatically under config/fiw_bosses/
3. Copy an example boss into the bosses folder
4. Reload configs in-game
5. Spawn your boss

In-game commands let you spawn, list, kill, and reload bosses and custom minions on the fly — full reference on GitHub.

Minion System

Custom minions sit alongside bosses in the config folder — each one a JSON file with its own stats, skin, equipment, abilities from the 42-ability pool, loot drops, and AI behavior. Bosses summon them by ID through the summon-minions ability, or you can spawn one directly via command.

Cross-Version Parity

Every config written for any version of the mod works on every other version, byte-for-byte. The Fabric 1.21.11 port handles Minecraft's newer DataComponents API behind the scenes — your JSON keeps using the same enchantments, display names, custom model data, and attribute modifiers it always did, and they take effect identically on every loader.

Requirements

NeoForge 1.21.1 (active)

Minecraft 1.21.1 NeoForge 21.1.x Java 21 Server-side only Yes

Fabric 1.21.11 (active)

Minecraft 1.21.11 Fabric Loader 0.18.1 or newer Fabric API 0.141.3+1.21.11 or newer Java 21 Server-side only Yes

Fabric 1.20.1 (legacy)

Minecraft 1.20.1 Fabric Loader 0.18.3 or newer Fabric API 0.92.2+1.20.1 Java 21 Server-side only Yes

Documentation

Full configuration reference with all fields, ability parameters, and examples available on the GitHub repository.

License

GNU General Public License v3.0

Made by Fi3w0 — built for a private SMP, shared with everyone. Developed with assistance from Claude Opus 4.8.