MythicMobs, Creating Your First Custom Boss

What Makes a Boss in MythicMobs?

A boss in MythicMobs is a custom mob definition with enhanced stats, unique skills, and curated drop tables. Unlike vanilla mobs, a MythicMobs boss can have thousands of health points, cast area-of-effect abilities, summon minions, and drop custom loot. This mythicmobs custom boss tutorial walks you through creating one from scratch.

File Structure

MythicMobs configs live in plugins/MythicMobs/Mobs/, plugins/MythicMobs/Skills/, and plugins/MythicMobs/DropTables/. You can organize files however you want; MythicMobs loads all YAML files in each folder recursively.

Step 1: Define the Mob

Create a file called plugins/MythicMobs/Mobs/forest_guardian.yml:

ForestGuardian:
  Type: ZOMBIE
  Display: "&2Forest Guardian"
  Health: 500
  Damage: 12
  Armor: 10
  Options:
    MovementSpeed: 0.25
    PreventOtherDrops: true
    PreventSunburn: true
  Equipment:
    - DIAMOND_SWORD HAND
    - CHAINMAIL_CHESTPLATE CHEST
    - CHAINMAIL_LEGGINGS LEGS
    - CHAINMAIL_BOOTS FEET
  Skills:
    - skill{s=ForestGuardianSkills} @self ~onSpawn
    - skill{s=PoisonAura} @PlayersInRadius{r=8} ~onTimer:100
    - skill{s=RootSlam} @target ~onTimer:200
  Drops:
    - forest_guardian_drops

This creates a zombie-based boss with 500 HP, custom equipment, and three skill triggers. The ~onTimer mechanic fires skills at intervals (100 ticks = 5 seconds, 200 ticks = 10 seconds).

Step 2: Create the Skills

Create plugins/MythicMobs/Skills/forest_guardian_skills.yml:

ForestGuardianSkills:
  Skills:
    - message{msg="&2The Forest Guardian awakens!"} @PlayersInRadius{r=30}
    - effect:particles{p=VILLAGER_HAPPY;a=50;s=0.5} @self

PoisonAura:
  Skills:
    - potion{t=POISON;d=60;l=1} @PlayersInRadius{r=8}
    - effect:particles{p=SPELL_WITCH;a=30;s=1} @self
    - sound{s=entity.wither.ambient;v=0.5;p=0.8} @self

RootSlam:
  Conditions:
    - lineofsight true
  Skills:
    - damage{a=8}
    - potion{t=SLOW;d=40;l=3} @target
    - effect:particles{p=BLOCK_CRACK;m=OAK_LOG;a=40;s=0.3} @target
    - sound{s=entity.iron_golem.attack;v=1;p=0.6} @target

The PoisonAura skill applies poison to all players within 8 blocks. RootSlam targets the boss's current target, deals damage, slows them, and plays a log-cracking particle effect.

Step 3: Configure Drops

Create plugins/MythicMobs/DropTables/forest_guardian_drops.yml:

forest_guardian_drops:
  TotalItems: 3
  Drops:
    - DIAMOND 1-3 1
    - EMERALD 2-5 0.8
    - GOLDEN_APPLE 1 0.3
    - exp 200-500
    - money 100-250

The numbers after each item are: amount (or range), then drop chance (1 = 100%, 0.3 = 30%). TotalItems: 3 caps the total item drops at three, so the boss does not shower loot.

Step 4: Spawn the Boss

# Spawn manually
/mm mobs spawn ForestGuardian

# Spawn at specific coordinates
/mm mobs spawn ForestGuardian 1 world,100,65,200

# Set up a timed spawner
/mm spawners create ForestGuardianSpawner ForestGuardian
/mm spawners set ForestGuardianSpawner cooldown 3600
/mm spawners set ForestGuardianSpawner maxmobs 1

The spawner respawns the boss every 3600 seconds (1 hour) with a max of 1 active at a time. This mythicmobs custom boss tutorial spawner setup prevents stacking multiple bosses in one area.

Step 5: Test and Tune

1. Spawn the boss in a flat test area.
2. Check health: /mm mobs info ForestGuardian.
3. Fight it. Adjust Health, Damage, and skill timers based on difficulty.
4. Verify drops by killing the boss several times.
5. Run /mm reload after every config change.

Tips for Better Bosses

• Add a BossBar option to show a health bar at the top of the screen: BossBar: true under Options.
• Use ~onDamaged triggers for reactive skills like counter-attacks or phase transitions.
• Combine with WorldGuard regions to prevent bosses from wandering out of their arena. See for region setup.
• Scale difficulty by adding conditions like - playercount{a=><4>} to activate harder skills when more players are present.

For installing MythicMobs itself, start with How to Install MythicMobs. For advanced skill chaining, see MythicMobs Skill Tree Explained.

See these configs in action: Astroworld MC, IP play.astroworldmc.com, Java + Bedrock.