Monster Mash - Ability ID 516

In-Game Description

"Casts Trick-or-Treat on entry."

Extended In-Game Description

For use in Elite Redux extended ability UI (280-300 chars max)

Automatically casts Trick-or-Treat when entering battle, adding Ghost as a third type to the target Pokemon. This removes Ghost immunity to physical attacks in Fog weather and adds Ghost weaknesses. The effect persists until the target switches out, making it a powerful counter to Fog teams.

Character count: 292

Detailed Mechanical Explanation

For Discord/reference use

Core Mechanics

Monster Mash automatically casts Trick-or-Treat when the user enters battle, targeting the opposing Pokemon. This ability uses the UseEntryMove function with MOVE_TRICK_OR_TREAT and 0 power.

Implementation:

constexpr Ability MonsterMash = {
    .onEntry = +[](ON_ENTRY) -> int { return UseEntryMove(battler, ability, MOVE_TRICK_OR_TREAT, 0); },
};

How Trick-or-Treat Works

Trick-or-Treat is a Status move with the following properties:

• Effect: EFFECT_THIRD_TYPE
• Type: Ghost
• Accuracy: 100
• PP: 20
• Target: Selected opposing Pokemon
• Flags: Protect-affected, Mirror Move-affected

When successful, Trick-or-Treat:

1. Adds Ghost as a third type to the target
2. Sets the trickOrTreat flag in the target's volatile struct
3. The effect remains until the target switches out

Fog Weather Interaction (Critical)

This is the most important tactical aspect of Monster Mash. In Fog weather:

Normal Ghost-types in Fog:

// From battle_util.c
if (IS_BATTLER_OF_TYPE(battlerDef, TYPE_GHOST) && 
    IsBattlerWeatherAffected(battlerDef, WEATHER_FOG_ANY) && 
    !gVolatileStructs[battlerDef].trickOrTreat)
    MUL_MODIFIER(&modifier, .8);

• Ghost-types in Fog receive a 0.8x multiplier to physical damage taken (20% reduction)
• This makes them effectively immune to physical attacks

After Trick-or-Treat:

• The trickOrTreat flag is set to TRUE
• The condition !gVolatileStructs[battlerDef].trickOrTreat becomes FALSE
• The Ghost-type no longer receives the 0.8x damage reduction in Fog
• They take full damage from physical attacks

This creates a unique strategic niche where Monster Mash can neutralize Ghost-types' Fog weather immunity.

Activation Conditions

• Triggers immediately upon switching in
• Does not trigger if the user is already on the field
• Can fail if:
  • The target is already Ghost-type (naturally, not from Trick-or-Treat)
  • The target is protected by Protect/Detect
  • The target has already been affected by Trick-or-Treat

Type Interaction Changes

After Trick-or-Treat adds Ghost type:

• Target gains Ghost STAB if using Ghost moves
• Target becomes weak to Ghost and Dark moves
• Target becomes immune to Normal and Fighting moves (unless they have Scrappy or similar)
• Target becomes immune to trapping moves/abilities
• In Fog: Target LOSES Ghost-type physical damage immunity

Strategic Implications

1. Fog Counter: Primary use is removing Ghost-types' physical immunity in Fog
2. Type Manipulation: Can give opponents unwanted Ghost weaknesses
3. Entry Hazard: Automatic effect on switch-in provides immediate pressure
4. Defensive Liability: Can make non-Ghost types vulnerable to Ghost/Dark coverage

Example Scenarios

• Vs Ghost in Fog: Phanfernal switches in against Gengar in Fog. Monster Mash applies Trick-or-Treat, removing Gengar's physical damage immunity. Now physical attackers can hit Gengar for full damage.
• Vs Non-Ghost: Phanfernal switches in against Garchomp. Trick-or-Treat adds Ghost type, making Garchomp weak to Ghost/Dark but immune to Fighting coverage.

Common Users

• Phanfernal: Fire/Grass type with Monster Mash as an innate ability
• Crabonination: Has Monster Mash as one of its innate abilities

Competitive Usage Notes

• Best used in Fog-heavy teams to counter opposing Ghost-types
• Pairs well with physical attackers who struggle against Ghosts in Fog
• Can disrupt defensive Ghost-types relying on Fog immunity
• Less useful outside of Fog weather
• Consider the risk of giving opponents Ghost STAB

Counters

• Magic Bounce reflects Trick-or-Treat back
• Switching out removes the effect
• Natural Ghost-types are unaffected
• Protect/Detect blocks the initial cast
• Taunt prevents manual Trick-or-Treat but not Monster Mash

Synergies

• Fog setters: Maximize the ability's anti-Ghost utility
• Physical attackers: Benefit from removing Ghost immunity
• Pursuit users: Trap Ghost-types trying to switch out
• Ghost/Dark coverage: Exploit the new weakness
• Arena Trap/Shadow Tag: Prevent switching to maintain the effect