Link Procedure Guide

Link scripts are built around Link Rating, Link Materials, and zones pointed to by Link Markers. A normal Link Monster registers a rule Summon procedure in the Extra Deck. During that procedure, the player selects a legal material group, the selected cards are recorded as materials, and the helper sends them to the GY with REASON_MATERIAL+REASON_LINK.

Effects can also make a player Link Summon during resolution. Those effects should still ask the chosen Link Monster whether the current material group is legal before calling the core Summon function.

The Three Jobs

Job	Where it usually lives	What it does
Link Monster procedure	The Link Monster script in `initial_effect`	Registers an `EFFECT_SPSUMMON_PROC` in the Extra Deck with `SUMMON_TYPE_LINK`.
Effect that performs a Link Summon	A Spell, Trap, or monster effect	Checks `Card.IsLinkSummonable`, then calls `Duel.LinkSummon`.
Link Marker and linked-zone effects	Usually on a Link Monster after it is on the field	Reads linked groups, linked zones, mutual links, columns, or Link Material properties.

For a normal Link Monster, start with the first job. The procedure is what teaches the engine how that monster can be Link Summoned.

Standard Link Procedure

Beat Cop from the Underworld (c99011763.lua) has the simplest "2 monsters" shape:

lua

function c99011763.initial_effect(c)
    c:EnableReviveLimit()
    aux.AddLinkProcedure(c,nil,2,2)
end

Read that as:

Piece	Meaning
`aux.AddLinkProcedure`	Registers the Link Summon procedure on the Extra Deck monster.
`nil`	No extra material filter; any legal Link Material can be used.
`2`	Minimum number of material cards selected.
`2`	Maximum number of material cards selected.
`c:EnableReviveLimit()`	Marks the Link Monster as needing a proper Summon before it can be revived by ordinary revive effects.

Cyberse Witch (c11674673.lua) shows the same pattern with a per-material filter:

lua

aux.AddLinkProcedure(c,aux.FilterBoolFunction(Card.IsLinkRace,RACE_CYBERSE),2,2)
c:EnableReviveLimit()

The filter is checked on each candidate material. Here, each material must be a Cyberse Link Material according to Card.IsLinkRace.

Helper Arguments

The standard helper is:

lua

aux.AddLinkProcedure(c,f,min,max,gf)

Argument	Meaning
`c`	The Link Monster receiving the procedure.
`f`	Optional per-material filter. `nil` means no extra Type, Race, Attribute, Set, or name restriction.
`min`	Minimum number of material cards the player must select.
`max`	Optional maximum number of material cards. When omitted, local `procedure.lua` uses `c:GetLink()`.
`gf`	Optional whole-group check. Use this for text that depends on the selected group as a whole.

Exceed the Pendulum (c92812851.lua) uses a group check:

lua

aux.AddLinkProcedure(c,aux.FilterBoolFunction(Card.IsType,TYPE_EFFECT),2,99,s.gchk)

function s.gchk(g)
    return g:IsExists(Card.IsType,1,nil,TYPE_PENDULUM)
end

The per-card filter requires every material to be an Effect Monster. The group check then requires at least one selected material to be a Pendulum Monster. This is a common split: use f for "each material must be..." and gf for "among those materials, the full group must also..."

What The Helper Builds

Local procedure.lua creates and registers this procedure:

lua

local e1=Effect.CreateEffect(c)
e1:SetDescription(1166)
e1:SetType(EFFECT_TYPE_FIELD)
e1:SetCode(EFFECT_SPSUMMON_PROC)
e1:SetProperty(EFFECT_FLAG_CANNOT_DISABLE+EFFECT_FLAG_UNCOPYABLE)
e1:SetRange(LOCATION_EXTRA)
e1:SetCondition(Auxiliary.LinkCondition(f,min,max,gf))
e1:SetTarget(Auxiliary.LinkTarget(f,min,max,gf))
e1:SetOperation(Auxiliary.LinkOperation(f,min,max,gf))
e1:SetValue(SUMMON_TYPE_LINK)
c:RegisterEffect(e1)

This is a rule procedure, not an activated effect. It does not make a Chain Link. The core asks the condition whether a legal Link Summon exists, the target branch lets the player choose Link Materials, and the operation branch moves those materials.

The helper refuses its procedure for a face-up Pendulum Link Monster in the Extra Deck. That check is directly in Auxiliary.LinkCondition.

Link Rating And Material Count

min and max limit the number of cards selected. They are not the total Link Rating. The total Link Rating check happens separately:

lua

sg:CheckWithSumEqual(Auxiliary.GetLinkCount,lc:GetLink(),#sg,#sg)

That line means: the selected group must be able to sum to the Link Monster's Link Rating, using one count value per selected card.

Local Auxiliary.GetLinkCount gives ordinary materials a value of 1. A Link Monster with Link Rating greater than 1 can count as either 1 or its own Link Rating. The helper encodes that choice for Group.CheckWithSumEqual.

That is why a Link-4 with min=2,max=4 can usually accept:

Selected materials	Why the sum can work
Four non-Link monsters	`1+1+1+1=4`
One Link-2 and two non-Link monsters	`2+1+1=4`
One Link-3 and one non-Link monster	`3+1=4`
Two Link-2 monsters	`2+2=4`

The selected card count must still stay inside min and max. A Link-4 helper with min=3,max=4 would not accept only two Link-2 monsters, even though their Link Rating sum can equal 4.

Material Pool

The ordinary material pool comes from your Monster Zone:

lua

local mg=Duel.GetMatchingGroup(Auxiliary.LConditionFilter,tp,LOCATION_MZONE,0,nil,f,lc,e)

Auxiliary.LConditionFilter checks that the card:

is face-up if it is on the field, unless the procedure effect has EFFECT_FLAG_SET_AVAILABLE
can be used as Link Material for the Link Monster through Card.IsCanBeLinkMaterial
passes the optional per-material filter f

If an effect calls Duel.LinkSummon with a material group, the helper filters that group instead of starting from the whole Monster Zone.

Local Link procedures also account for:

mandatory Link Materials through EFFECT_MUST_BE_LMATERIAL
Extra Monster Zone and Main Monster Zone availability through Duel.GetLocationCountFromEx
optional whole-group checks through gf(sg,lc,tp)
fixed required material through the lmat argument used by effect-driven Link Summons
extra Link Material effects through EFFECT_EXTRA_LINK_MATERIAL

Auxiliary.GetLinkMaterials can include extra candidates from the hand, Spell & Trap Zone, or opponent's field only when a related EFFECT_EXTRA_LINK_MATERIAL effect says that candidate is usable. The procedure then checks compatibility again after the group is selected and consumes the extra-material effect's count limit with te:UseCountLimit(tp).

Operation Order

The ordinary operation is short and important:

lua

local g=e:GetLabelObject()
c:SetMaterial(g)
Auxiliary.LExtraMaterialCount(g,c,tp)
Duel.SendtoGrave(g,REASON_MATERIAL+REASON_LINK)
g:DeleteGroup()

The selected group was kept alive by the target branch, then stored on the procedure effect. During operation:

Card.SetMaterial records the group as the Link Monster's materials.
Auxiliary.LExtraMaterialCount consumes compatible extra-material count limits.
Duel.SendtoGrave sends the selected cards to the GY with REASON_MATERIAL+REASON_LINK.
The kept-alive group is deleted.

Unlike Xyz Summons, Link Materials do not become overlay materials under the new monster. A normal Link procedure sends them to the GY.

Effects That Link Summon

World Legacy Awakens (c12989604.lua) is a clean Spell example. It asks the Extra Deck for any Link Monster that is currently Link Summonable:

lua

function c12989604.filter(c)
    return c:IsLinkSummonable(nil)
end

function c12989604.target(e,tp,eg,ep,ev,re,r,rp,chk)
    if chk==0 then
        return Duel.IsExistingMatchingCard(c12989604.filter,tp,LOCATION_EXTRA,0,1,nil)
    end
    Duel.SetOperationInfo(0,CATEGORY_SPECIAL_SUMMON,nil,1,0,0)
end

function c12989604.activate(e,tp,eg,ep,ev,re,r,rp)
    Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_SPSUMMON)
    local g=Duel.SelectMatchingCard(tp,c12989604.filter,tp,LOCATION_EXTRA,0,1,1,nil)
    local tc=g:GetFirst()
    if tc then
        Duel.LinkSummon(tp,tc,nil)
    end
end

The nil material group means "use that Link Monster's normal material pool." The selected Link Monster's registered procedure still performs final material selection and movement.

Prank-Kids Plan (c15447747.lua) uses a restricted material group:

lua

function c15447747.matfilter(c)
    return c:IsFaceup() and c:IsSetCard(0x120)
end

function c15447747.lkfilter(c,mg)
    return c:IsSetCard(0x120) and c:IsLinkSummonable(mg)
end

function c15447747.lkop(e,tp,eg,ep,ev,re,r,rp)
    local mg=Duel.GetMatchingGroup(c15447747.matfilter,tp,LOCATION_MZONE,0,nil)
    Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_SPSUMMON)
    local tg=Duel.SelectMatchingCard(tp,c15447747.lkfilter,tp,LOCATION_EXTRA,0,1,1,nil,mg)
    local tc=tg:GetFirst()
    if tc then
        Duel.LinkSummon(tp,tc,mg)
    end
end

Here, the effect only permits face-up Prank-Kids monsters you control as the material group. The Extra Deck filter receives that group and asks each Prank-Kids Link Monster whether it can be Link Summoned with it.

The core bindings for Card.IsLinkSummonable and Duel.LinkSummon both reject use during the Damage Step. Duel.LinkSummon yields to the core and returns no Lua value.

Fixed Required Material

Some effects require a specific card to be used as Link Material. Outburst Dragon (c87263576.lua) does that with the lcard argument:

lua

function c87263576.lkfilter(c,lc)
    return c:IsRace(RACE_DRAGON) and c:IsLinkSummonable(nil,lc)
end

function c87263576.lkop(e,tp,eg,ep,ev,re,r,rp)
    local c=e:GetHandler()
    if c:IsControler(1-tp) or not c:IsRelateToEffect(e) or c:IsFacedown() then return end
    local g=Duel.GetMatchingGroup(c87263576.lkfilter,tp,LOCATION_EXTRA,0,nil,c)
    if g:GetCount()>0 then
        Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_SPSUMMON)
        local sg=g:Select(tp,1,1,nil)
        Duel.LinkSummon(tp,sg:GetFirst(),nil,c)
    end
end

The fourth argument to Duel.LinkSummon is the required material. In Auxiliary.LinkCondition, that card is added to the material pool only if it passes the Link Material filter, and Auxiliary.LCheckGoal requires the final selected group to contain it.

Use this shape when the effect text says to immediately Link Summon using that specific monster.

Using An Opponent's Monster

Unchained Soul of Disaster (c89019964.lua) shows a controlled way to use an opponent's monster as part of the temporary material group:

lua

function c89019964.tgfilter(c,tp,ec)
    local mg=Group.FromCards(ec,c)
    return c:IsFaceup() and Duel.IsExistingMatchingCard(c89019964.lfilter,tp,LOCATION_EXTRA,0,1,nil,mg)
end

function c89019964.lfilter(c,mg)
    return c:IsAttribute(ATTRIBUTE_DARK) and c:IsLinkSummonable(mg,nil,2,2)
end

function c89019964.operation(e,tp,eg,ep,ev,re,r,rp)
    local c=e:GetHandler()
    local tc=Duel.GetFirstTarget()
    if c:IsFaceup() and c:IsRelateToEffect(e) and c:IsControler(tp)
        and tc:IsFaceup() and tc:IsRelateToEffect(e) and tc:IsControler(1-tp)
        and not tc:IsImmuneToEffect(e) then
        local mg=Group.FromCards(c,tc)
        Duel.Hint(HINT_SELECTMSG,tp,HINTMSG_SPSUMMON)
        local g=Duel.SelectMatchingCard(tp,c89019964.lfilter,tp,LOCATION_EXTRA,0,1,1,nil,mg)
        local lc=g:GetFirst()
        if lc then
            Duel.LinkSummon(tp,lc,mg,nil,2,2)
        end
    end
end

The operation rebuilds the exact two-card group at resolution and checks that both monsters are still face-up, related, controlled by the expected players, and not immune to the effect. That is the habit to copy: do not trust a target chosen earlier if the field can change before resolution.

Reading Linked Zones

Link Monsters often need to know which zones their Link Markers point to. Gorgon of Zilofthonia (c12067160.lua) uses several linked-zone APIs:

lua

function s.zonelimit(e)
    return 0x7f007f & ~e:GetHandler():GetLinkedZone()
end

function s.antg(e,c)
    return e:GetHandler():GetLinkedGroup():IsContains(c)
end

function s.discon(e,tp,eg,ep,ev,re,r,rp)
    local rc=re:GetHandler()
    return rc and re:IsActiveType(TYPE_MONSTER) and rc:IsRelateToChain()
        and e:GetHandler():GetLinkedGroup():IsContains(rc)
        and rc:IsCanBeDisabledByEffect(e) and Duel.IsChainDisablable(ev)
end

Use Card.GetLinkedGroup when you need the actual cards in linked zones. Use Card.GetLinkedZone when you need the zone mask itself.

Cyberse Witch also shows why the optional player argument matters:

lua

function c11674673.thcfilter(c,ec)
    if c:IsLocation(LOCATION_MZONE) then
        return ec:GetLinkedGroup():IsContains(c)
    else
        return bit.extract(ec:GetLinkedZone(c:GetPreviousControler()),c:GetPreviousSequence())~=0
    end
end

The card was Special Summoned and may no longer be in the same place by the time the trigger checks the event group. Passing c:GetPreviousControler() asks for the linked-zone mask from the relevant player's perspective, then bit.extract checks the previous sequence.

For field-wide checks, use Duel.GetLinkedZone or Duel.GetLinkedGroup. For mutual-link effects, use the mutual versions: Card.GetMutualLinkedGroup, Card.GetMutualLinkedZone, and their count helpers.

Material Memory

After a successful Link Summon, the new Link Monster can inspect its materials with Card.GetMaterial. Beat Cop from the Underworld uses EFFECT_MATERIAL_CHECK to remember whether its materials had different names and included at least two DARK materials:

lua

function c99011763.valcheck(e,c)
    local g=c:GetMaterial()
    if g:GetClassCount(Card.GetLinkCode)==g:GetCount()
        and g:IsExists(Card.IsLinkAttribute,2,nil,ATTRIBUTE_DARK) then
        e:GetLabelObject():SetLabel(1)
    else
        e:GetLabelObject():SetLabel(0)
    end
end

Use Link-specific identity helpers when material text cares about Link Material properties:

Helper	Use
`Card.GetLinkCode`	Material name/code while used for a Link Summon.
`Card.IsLinkCode`	Code check using Link Material identity.
`Card.IsLinkRace`	Race check using Link Material identity.
`Card.IsLinkAttribute`	Attribute check using Link Material identity.
`Card.IsLinkType`	Type check using Link Material identity.

Common Pitfalls

Mistake	Better habit
Forgetting `EnableReviveLimit` on a Link Monster.	Put it near `aux.AddLinkProcedure` in `initial_effect`.
Treating `min` and `max` as Link Rating limits.	Read them as the number of selected material cards. Link Rating is checked with `Auxiliary.GetLinkCount`.
Assuming every Link Monster material always contributes its Link Rating.	A Link Monster with Link Rating greater than 1 may count as 1 or its Link Rating.
Sending materials manually in an effect before calling `Duel.LinkSummon`.	Let the selected Link Monster's procedure choose, record, and send materials.
Calling `Duel.LinkSummon` without a matching `Card.IsLinkSummonable` check.	Check the Extra Deck candidates first, then recheck or rebuild the group in the operation if the field may have changed.
Forgetting that `Duel.LinkSummon` has no Lua return value.	Put follow-up logic in later events or structure the effect around the Summon itself.
Using a target-branch material group after resolution changes.	Rebuild the group in the operation and verify cards are still face-up, related, and controlled correctly.
Checking linked zones with the wrong player perspective.	Pass the player argument to `GetLinkedZone` when previous controller or opponent perspective matters.
Confusing linked cards with linked zone masks.	Use `GetLinkedGroup` for cards and `GetLinkedZone` for bitmasks.
Trying to Link Summon during the Damage Step.	Local core rejects `Card.IsLinkSummonable` and `Duel.LinkSummon` during the Damage Step.

Link Procedure Guide ​

The Three Jobs ​

Standard Link Procedure ​

Helper Arguments ​

What The Helper Builds ​

Link Rating And Material Count ​

Material Pool ​

Operation Order ​

Effects That Link Summon ​

Fixed Required Material ​

Using An Opponent's Monster ​

Reading Linked Zones ​

Material Memory ​

Common Pitfalls ​

Useful API Pages ​