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Spawner modifiers

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OfficialRell edited this page Sep 7, 2026 · 11 revisions

Spawner modifiers are special items that players can apply to a spawner to change how it behaves.

Examples include reducing the health of spawned mobs, applying potion effects, or adjusting the value of a spawner upgrade. Each modifier is configured in the modifiers.yml file.

Modifiers can be applied to a spawner in the upgrade GUI by clicking on the modifier in the bottom inventory. Modifiers can be removed by clicking on the modifier item in the upgrade GUI.

A modifier stays active on the spawner until it runs out of usages (if a usage limit is set), or until the player removes it.

Creating a modifier

Every modifier is defined under the Modifiers section and is identified by a unique key.

The file contains one example modifier – generic. To add a new modifier, copy the entire generic block and paste it below, then change generic to your chosen key and adjust the values.

Modifiers:
  generic:       # the modifier key
    display: ...
    item: ...
    requirements: ...
    effect: ...
 
  new_modifier:   # your new modifier
    display: ...
    ...

Modifier structure

Display name

display: "<red-#ffbf00>Health reduction"

A name shown to players when they apply or remove the modifier.

Item

Defines the modifier item that will be given to players.

item:
  material: PAPER
  name: "<#red-#ffbf00>Health reduction modifier <#bfffff>(-%value%%)"
  lore:
  - ""
  - "<#8fbfbf><!italic>Reduces mob health by %value% percent"
  - "  <#8fbfbf><!italic>upon spawning."
  model: 0
  glint: true
  • material - item material type.
  • name - display name, supports placeholders (see Parameters and placeholders).
  • lore - item description, supports placeholders.
  • model - custom model data value, set to 0 to disable.
  • glint - whether the item has enchantment glint

Requirements

Requirements control which spawners a modifier can be applied to.

requirements:
  spawner-level:
    level: 0
    ignore: []
  spawner-types:
    list: []
    exclude: false
  • spawner-level:
    • level - minimum spawner level required before this modifier can be applied; a spawner's level equals the total number of upgrade levels across all of its upgrades, except ignored ones (e.g. a spawner with no upgrades is level 0; one level-up in each of the 6 upgrade types makes it level 6). You can use * %required_level% placeholder in the item name or lore to display this number.
    • ignore - list of upgrade types that will not count towards the required level (e.g. [DELAY, NEARBY]); Leave empty ([]) to allow all upgrade types.
  • spawner-types:
    • list - list of spawner types this modifier can be applied to (e.g. [ZOMBIE, SKELETON]); Leave empty ([]) to allow all spawner types.
    • exclude - when true the list becomes a blacklist.

Effect

The effect section defines what the modifier does. The required fields vary by effects — see built-in effects below.

effect:
  id: change-attribute
  attribute: health
  evaluate-type: SUBTRACT_PERCENT

Built-in effects

Parameters required when giving a modifier item for all effects:

  • usage - how many times this modifier activates before it stops working; use #infinite for unlimited activations.
  • chance - chance (1–100) that the modifier activates each time a mob spawns; use 100 for it to always activate.

change-attribute

Modifies a specific attribute of spawner summoned mobs.

effect:
  type: change-attribute
  attribute: <attribute>
  evaluate-type: <evaluate type>

See attributes and evaluate types.

Parameters required when giving a modifier item:

  • value - amount to apply (must be greater than 0).

change-upgrade

Modifies the value of one of the spawner's upgrades — for example, increasing the spawn range or decreasing the spawn delay.

effect:
  id: change-upgrade
  evaluate-type: <evaluate type>
  upgrade-type: <upgrade type>

See evaluate types and upgrade types.

Parameters required when giving a modifier item:

  • value - amount to apply to the upgrade value (must be greater than 0).

apply-effect

Applies a potion effect to spawner summoned mobs.

effect:
  id: apply-effect
  potion-type: <potion type>

See potion types.

Parameters required when giving a modifier item:

  • duration - how long the potion effect lasts, in ticks (20 ticks = 1 second); use #infinite for an infinite duration; must be greater than 0.
  • amplifier - strength level of the effect (e.g. 1 = level I, 2 = level II); must be greater than 0.
  • ambient - should the effect be ambient (more and slightly translucent).
  • particles - should the effect produce particles.

disable-ai

Disables the ai of spawner summoned mobs (unable to move or attack, but can be pushed).

effect:
  id: disable-ai

No additional parameters required

set-fire

Set spawner summoned mobs on fire.

effect:
  id: set-fire

Parameters required when giving a modifier item:

  • ticks - how long the fire will last, in ticks (20 ticks = 1 second)

set-silent

Sets spawner summoned mobs silent.

effect:
  id: set-silent

No additional parameters required

set-glowing

Sets spawner summoned mobs have a glowing effect.

effect:
  id: set-glowing

No additional parameters required

Parameters and placeholders

When a modifier item is given to a player via a command, the command includes parameter values (e.g. the value reduction amount or number of usages). These values can be displayed in the item's name and lore using placeholders.

Placeholder Description
%usage% number of activations remaining. Displays ∞ when set to infinite
%chance% activation chance percentage
%value% effect value (e.g. percentage or flat amount)
%duration% potion effect duration in seconds. Displays ∞ when set to infinite
%amplifier% potion effect level
%ambient% true or false
%particles% true or false
%required_level% minimum spawner level required to apply this modifier

Note! That some placeholders will display regular numbers, but for some you might want to display Roman numerals, that can be done by adding :r after the placeholder (e.g. %amplifier:r%), and for values that use ticks you might want to display seconds, that can be my adding :sn after the placeholder (e.g. %duration:s0%) where n is the decimal points.

Examples

Below is a complete modifiers.yml with two modifiers: one that reduces mob health and one that applies a poison effect.

Modifiers:
  health_reduction:
    display: "<red>Health reduction"
    effect:
      id: change-attribute
      attribute: health
      evaluate-type: SUBTRACT_PERCENT
   item:
     material: PAPER
     name: "<red>Health reduction <gray>(-%value%%)"
     lore:
     - ""
     - "<gray>Reduces mob health by %value%%"
     - "<gray>Usages: %usage%"
     - "<gray>Chance: %chance%%"
     model: 0
     glint: true
 
  poison_spawner:
    display: "<green>Poison spawner"
    effect:
      id: apply-effect
      potion-type: poison
    requirements:
      spawner-level:
        level: 3
      spawner-types:
        list: [ZOMBIE, SKELETON, CREEPER]
    item:
      material: FERMENTED_SPIDER_EYE
      name: "<green>Poison modifier <gray>(Poison %amplifier:r%)"
      lore:
      - ""
# have to use %duration:s0% with the ':s0' to convert ticks into seconds, with no decimal point
      - "<gray>Applies Poison %amplifier:r% for %duration:s0%s"
      - "<gray>to each spawned mob."
      - "<gray>Usages: %usage%"
      - "<gray>Chance: %chance%%"
      - ""
      - "<yellow>Requires spawner level %required_level%"
      - "<yellow>Only applies to Zombies, Skeletons and Creepers"
      model: 0
      glint: true

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