It must be some special circumstance then. here is an example that works. It is a weapon that calls a spelldef.
<GameItemType InternalName="Reliquary_Mindkiller">
<REQtype>Sword</REQtype>
<REQmod>10 Weight
+17 Cutting attack
+2 Initiative
Each time this weapon strikes an enemy target 3 Spell Mastery and Spell Resist is drained from target and given to wielder for 10 round. Stacks.</REQmod>
<DisplayName>Mindthief</DisplayName>
<Description>Reliquary Item #76. What looks like an ordinary Scinan broadword. The sword has the incredible effect of "stealing" thoughts from whoever it cuts. The thoughts will appear in the wielder's mind as if he or she had thought it themselves, but still easily identifiable as belonging to someone else. The person who has the thoughts stolen experience severe discomfort, some say it even wounds their soul temporarily. The person who wields the sword may also experience a slight increase in intelligence briefly. Theoretically the sword holds an omnious power - in the wrong hands it could be used as a tyrant's tool. When used in combat, mostly things happen too fast for the stolen thoughts to be of any use to the wielder.</Description>
<Type>Weapon</Type>
<WeaponType>OneHanded</WeaponType>
<CanBeEquipped>1</CanBeEquipped>
<ShopValue>600</ShopValue>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_Attack_Cutting</StrVal>
<Value>17</Value>
</GameModifier>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_CombatSpeed</StrVal>
<Value>2</Value>
</GameModifier>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_CurrentWeight</StrVal>
<Value>10</Value>
</GameModifier>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>MeleeAppliesSpell</Attribute>
<StrVal>Reliquary_Mindkiller</StrVal>
<Provides>Each time this weapon strikes an enemy target 3 Spell Mastery and Spell Resist is drained from target and given to wielder for 10 rounds. Stacks.</Provides>
</GameModifier>
<IsAvailableForSovereignCustomization>0</IsAvailableForSovereignCustomization>
<Likelihood>250</Likelihood>
<RarityDisplay>Rare</RarityDisplay>
<HeroOnly>1</HeroOnly>
<IsAvailableForUnitDesign>0</IsAvailableForUnitDesign>
<Prereq>
<Type>UnitStat_Level</Type>
<Attribute>6</Attribute>
</Prereq>
<AIData AIPersonality="AI_General">
<AIPrefType>AIPrefType_CUTTING</AIPrefType>
<AIPriority>400</AIPriority>
</AIData>
<ArtDef>Broadsword_Champions_ArtDef</ArtDef>
</GameItemType>
the spelldef
<SpellDef InternalName="Reliquary_Mindkiller">
<DisplayName>Mindthief</DisplayName>
<Description>Each time struck by a Mindthief weapon reduces Spell Mastery and Spell Resist by 3</Description>
<Image>W_Broadsword_Scinan_Icon_01.png</Image>
<IconFG>W_Broadsword_Scinan_Icon_01.png</IconFG>
<IconBG>W_Broadsword_Scinan_Icon_01.png</IconBG>
<IconColor>255,103,2</IconColor>
<HideInHiergamenon>1</HideInHiergamenon>
<IsCastable>0</IsCastable>
<SpellType>Tactical</SpellType>
<SpellClass>Offensive</SpellClass>
<SpellSubClass>Damage</SpellSubClass>
<SpellTargetType>EnemyUnit</SpellTargetType>
<Radius>0</Radius>
<CanStack>1</CanStack>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_MagicResist</StrVal>
<Duration>10</Duration>
<Value>-3</Value>
</GameModifier>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_MagicResist</StrVal>
<Duration>10</Duration>
<ApplyToCaster>1</ApplyToCaster>
<Value>3</Value>
</GameModifier>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_MagicPower</StrVal>
<Duration>10</Duration>
<Value>-3</Value>
</GameModifier>
<GameModifier>
<ModType>Unit</ModType>
<Attribute>AdjustUnitStat</Attribute>
<StrVal>UnitStat_MagicPower</StrVal>
<Duration>10</Duration>
<ApplyToCaster>1</ApplyToCaster>
<Value>3</Value>
</GameModifier>
<AIData AIPersonality="AI_General">
<AIPriority>40</AIPriority>
</AIData>
<HitSoundFX>Spell_Fireball_01</HitSoundFX>
<SpellDefEffect>
<EffectName>T_Soulburning_Particle</EffectName>
<LocalPosition>0, 0 ,0</LocalPosition>
<EffectScale>0.50</EffectScale>
<EffectDelay>0.25</EffectDelay>
<SnapToTerrain>1</SnapToTerrain>
</SpellDefEffect>
</SpellDef>
It works just as stated, wearer gains 3 spell resist and 3 spell mastery for every time the enemy is stricken, and target loses 3 of both every time.
