MobEffects

MobEffects is a lightweight, vanilla-inspired Paper plugin that extends the existing Minecraft mechanic where spiders can spawn with potion effects.

In vanilla Minecraft, spiders have a small chance to spawn with effects such as Speed, Strength, Regeneration, or Invisibility.
MobEffects applies the same idea to other hostile mobs, without adding complex systems or altering core gameplay.

Configuration-driven design

MobEffects is fully configurable through config.yml.

Both the list of affected mobs and their potion effects can be freely modified.
The default configuration uses Zombie, Skeleton, and Creeper as examples, but these are not hard-coded limitations.

Server owners can:

• Add or remove mobs from the configuration
• Change effect lists and effect levels
• Adjust spawn chances and effect durations
• Switch between random or fixed effect application modes

No code changes or recompilation are required.

Default behavior

By default, effects are applied only when:

• The mob spawns naturally
• It is night time
• World difficulty is Normal or Hard
• A configurable chance check succeeds

The plugin does not modify mob AI, attributes, damage, drops, or behavior — it only applies potion effects.

Default mob setup

The following mobs and effects are used in the default configuration:

• Zombie — Speed, Strength
• Skeleton — Speed, Invisibility
• Creeper — Nausea, Slowness, Blindness, Weakness

Zombie and Skeleton effects are almost permanent, similar to vanilla spider effects.
Creeper effects last for a configurable random duration (30–45 seconds by default).

Effect modes

MobEffects supports two effect application modes:

• ALL — the mob receives all listed effects
• RANDOM_ONE — the mob receives one random effect, like vanilla spiders

Compatibility

MobEffects is designed to work alongside datapacks such as Upgraded Mobs.
It does not override or interfere with datapack mechanics and applies effects with a short delay to avoid conflicts.

Philosophy

MobEffects follows a vanilla-first design philosophy:

• Simple mechanics
• Predictable behavior
• Minimal performance impact

The goal is to make hostile mobs slightly more varied, while still feeling like part of vanilla Minecraft.