Field Spells

Field Spells are Spell Cards that live in the Field Zone. Their scripts usually combine a simple activation effect with always-on, triggered, or activated effects that only work while the card remains in LOCATION_FZONE.

Basic Field Spell Shape

Many Field Spells have a normal activation effect and then separate effects registered on the same card.

local e1=Effect.CreateEffect(c)
e1:SetType(EFFECT_TYPE_ACTIVATE)
e1:SetCode(EVENT_FREE_CHAIN)
c:RegisterEffect(e1)

local e2=Effect.CreateEffect(c)
e2:SetDescription(aux.Stringid(id,0))
e2:SetType(EFFECT_TYPE_IGNITION)
e2:SetRange(LOCATION_FZONE)
e2:SetCountLimit(1,id)
e2:SetTarget(s.target)
e2:SetOperation(s.operation)
c:RegisterEffect(e2)

The activation effect puts the Field Spell onto the field. The second effect is usable later because SetRange(LOCATION_FZONE) says the handler must be in the Field Zone.

Field Zone vs Spell & Trap Zone

Use LOCATION_FZONE when the script means the Field Zone as a concept:

e2:SetRange(LOCATION_FZONE)
local fc=Duel.GetFieldCard(tp,LOCATION_FZONE,0)

The local core stores the Field Zone inside Spell & Trap Zone internals, and the define file notes that a Field Spell can appear as Spell & Trap Zone sequence 5. You will see older or lower-level local scripts use:

local fc=Duel.GetFieldCard(tp,LOCATION_SZONE,5)

Prefer LOCATION_FZONE in learning code unless you are doing raw sequence or zone-mask work. See Field zones and sequences for the sequence details.

Effects While In The Field Zone

Field Spells can provide continuous field effects, trigger effects, and activated effects.

local e1=Effect.CreateEffect(c)
e1:SetType(EFFECT_TYPE_FIELD)
e1:SetCode(EFFECT_UPDATE_ATTACK)
e1:SetRange(LOCATION_FZONE)
e1:SetTargetRange(LOCATION_MZONE,LOCATION_MZONE)
e1:SetTarget(s.atktg)
e1:SetValue(300)
c:RegisterEffect(e1)

local e2=Effect.CreateEffect(c)
e2:SetType(EFFECT_TYPE_FIELD+EFFECT_TYPE_TRIGGER_O)
e2:SetCode(EVENT_PHASE+PHASE_END)
e2:SetRange(LOCATION_FZONE)
e2:SetTarget(s.target)
e2:SetOperation(s.operation)
c:RegisterEffect(e2)

Local c1003840.lua is a compact example: its activation effect is plain, then it registers an Ignition Effect and a field Trigger Effect with SetRange(LOCATION_FZONE).

The Card Providing The Effect Decides The Range

LOCATION_FZONE belongs on effects whose handler is the Field Spell. If an Equip Spell, monster, or Trap has an effect that cares about a Field Spell, that effect still uses the handler's own location.

Local c11881272.lua is a good crossing example. The Equip Spell has EFFECT_TYPE_EQUIP bonuses and also a Battle Phase trigger that can activate a Field Spell from the hand or Deck. That trigger uses SetRange(LOCATION_SZONE) because the handler is still the Equip Spell, not the Field Spell it will move later.

Activating Or Placing A Field Spell From The Deck

Some card effects place or activate a Field Spell from the Deck. Local scripts usually check the candidate's own activation effect before moving it:

function s.actfilter(c,tp)
    local te=c:GetActivateEffect()
    return c:IsType(TYPE_FIELD) and te and te:IsActivatable(tp,true,true)
end

During resolution, the common local pattern is:

local tc=Duel.SelectMatchingCard(tp,s.actfilter,tp,LOCATION_DECK,0,1,1,nil,tp):GetFirst()
if tc then
    local fc=Duel.GetFieldCard(tp,LOCATION_FZONE,0)
    if fc then
        Duel.SendtoGrave(fc,REASON_RULE)
        Duel.BreakEffect()
    end
    local te=tc:GetActivateEffect()
    if Duel.MoveToField(tc,tp,tp,LOCATION_FZONE,POS_FACEUP,true) then
        te:UseCountLimit(tp,1,true)
        local tep=tc:GetControler()
        local cost=te:GetCost()
        if cost then cost(te,tep,eg,ep,ev,re,r,rp,1) end
        Duel.RaiseEvent(tc,4179255,te,0,tp,tp,Duel.GetCurrentChain())
    end
end

This shape is visible in local Dream Mirror scripts such as c1050355.lua. Treat it as an advanced pattern to copy from a matching local script: the important beginner ideas are that the Field Spell's activation effect must be activatable, the existing Field Spell is handled by rule, and Duel.MoveToField uses LOCATION_FZONE. The numeric event in this pattern is part of existing local card-script handling for activating a Spell/Trap through another effect; do not invent a new number for beginner scripts.

Activate vs Place

Not every script that moves a Field Spell to the Field Zone activates that Field Spell's own activation effect.

Shape	Local pattern	What to copy
Activate a Field Spell through another effect	GetActivateEffect, IsActivatable, MoveToField, UseCountLimit, optional activation cost, then Duel.RaiseEvent	Copy from a matching local script such as c1050355.lua, c11881272.lua, or c97970833.lua.
Place a Field Spell face-up without activating it	Choose a Field Spell that can legally be placed, MoveToField, then add any temporary suppression or counter handling required by the card text	Copy from a matching local script such as c97254001.lua.

The second shape should not invent an activation event just because Duel.MoveToField was used. Local c97254001.lua places a Field Spell, adds a temporary EFFECT_CANNOT_TRIGGER, and transfers counters; it does not call the new card's activation cost or Duel.RaiseEvent.

Replacing The Existing Field Spell

When an effect puts a Field Spell into the Field Zone, the previous Field Spell may need to leave first. Local scripts often do this explicitly so the timing is clear and a Duel.BreakEffect() can separate the actions:

local fc=Duel.GetFieldCard(tp,LOCATION_FZONE,0)
if fc then
    Duel.SendtoGrave(fc,REASON_RULE)
    Duel.BreakEffect()
end
Duel.MoveToField(tc,tp,tp,LOCATION_FZONE,POS_FACEUP,true)

The local core also treats Duel.MoveToField(..., LOCATION_FZONE, ...) as a Field Zone placement and maps it to the correct Spell & Trap Zone slot internally.

Checking The Current Environment

Use Duel.IsEnvironment when a card cares whether a specific field or environment code is active.

if Duel.IsEnvironment(41418852,tp,LOCATION_FZONE) then
    -- Numeron Network is active in this player's Field Zone
end

The generated API page notes that the core checks face-up Field Zone cards first and can also match EFFECT_CHANGE_ENVIRONMENT state. Use Duel.GetFieldCard instead when you need the actual card object in the Field Zone.

Field Spells With Counters

Field Spells can permit and use counters like other cards.

function s.initial_effect(c)
    c:EnableCounterPermit(0x6e)
    -- effects
end

Local c97254001.lua stores counters on a Field Spell, moves another Field Spell into the Field Zone, then transfers counters if the new card can hold them. That pattern combines Field Zone replacement with counter scripting, so keep the two concerns separate when reading it.

Common Pitfalls

Mistake	Safer pattern
Registering later Field Spell effects with SetRange(LOCATION_SZONE).	Use LOCATION_FZONE unless you are deliberately writing raw Spell & Trap Zone sequence logic.
Giving an Equip Spell or monster effect SetRange(LOCATION_FZONE) because it places a Field Spell.	Use the handler's real location; only the Field Spell's own effects use LOCATION_FZONE.
Placing a Field Spell from the Deck without checking its activation effect.	Use c:GetActivateEffect() and te:IsActivatable(...) before moving it.
Calling UseCountLimit and Duel.RaiseEvent on a card that was only placed face-up.	Reserve that advanced sequence for effects that actually activate the Field Spell's own activation effect.
Forgetting the existing Field Spell.	Read it with Duel.GetFieldCard(tp,LOCATION_FZONE,0) and send it by rule when the local pattern requires explicit replacement.
Treating a Field Spell like an Equip Card.	Field Spells do not use Duel.Equip or EFFECT_EQUIP_LIMIT; they are Field Zone cards with effects in LOCATION_FZONE.
Using raw sequence 5 everywhere.	Prefer LOCATION_FZONE; reserve sequence 5 for zone/sequence lessons.

Useful API pages:

• Duel.MoveToField
• Duel.GetFieldCard
• Duel.IsEnvironment
• Duel.SendtoGrave
• Duel.BreakEffect
• Duel.RaiseEvent
• Duel.GetCurrentChain
• Card.GetActivateEffect
• Effect.UseCountLimit
• Effect.GetCost
• Effect.SetRange
• Effect.SetTargetRange
• Effect.SetValue