--ヴェノム·スワンプ
function c54306223.initial_effect(c)
	--Activate
	local e1=Effect.CreateEffect(c)
	e1:SetType(EFFECT_TYPE_ACTIVATE)
	e1:SetCode(EVENT_FREE_CHAIN)
	c:RegisterEffect(e1)
	--Add counter
	local e2=Effect.CreateEffect(c)
	e2:SetDescription(aux.Stringid(54306223,0))
	e2:SetCategory(CATEGORY_COUNTER)
	e2:SetType(EFFECT_TYPE_TRIGGER_F+EFFECT_TYPE_FIELD)
	e2:SetCode(EVENT_PHASE+PHASE_END)
	e2:SetCountLimit(1)
	e2:SetProperty(EFFECT_FLAG_REPEAT)
	e2:SetRange(LOCATION_SZONE)
	e2:SetOperation(c54306223.acop)
	c:RegisterEffect(e2)
	--atk down
	local e3=Effect.CreateEffect(c)
	e3:SetType(EFFECT_TYPE_FIELD)
	e3:SetCode(EFFECT_UPDATE_ATTACK)
	e3:SetRange(LOCATION_SZONE)
	e3:SetTargetRange(LOCATION_MZONE,LOCATION_MZONE)
	e3:SetValue(c54306223.atkval)
	c:RegisterEffect(e3)
	--destroy
	local e4=Effect.CreateEffect(c)
	e4:SetType(EFFECT_TYPE_FIELD)
	e4:SetCode(EFFECT_SELF_DESTROY)
	e4:SetRange(LOCATION_SZONE)
	e4:SetTargetRange(LOCATION_MZONE,LOCATION_MZONE)
	e4:SetTarget(Duel.VenomSwampCheck)
	c:RegisterEffect(e4)
end
function c54306223.atkval(e,c)
	return c:GetCounter(0x9)*-500
end
function c54306223.acop(e,tp,eg,ep,ev,re,r,rp)
	if not e:GetHandler():IsRelateToEffect(e) then return end
	for i=0,4 do
		local tc=Duel.GetFieldCard(tp,LOCATION_MZONE,i)
		if tc and tc:IsCanAddCounter(0x9,1) and not tc:IsSetCard(0x50) then
			tc:AddCounter(0x9,1)
		end
	end
	for i=0,4 do
		local tc=Duel.GetFieldCard(1-tp,LOCATION_MZONE,i)
		if tc and tc:IsCanAddCounter(0x9,1) and not tc:IsSetCard(0x50) then
			tc:AddCounter(0x9,1)
		end
	end
end
