Darklings have the same mechanic and result this patch, I also thought this was a bug. I believe that in a prior patch I tried fire dart on a ophidian and failed... is it supposed to succeed? That's news to me!

I think I read somewhere that "Immune to magic" was a boost to spell resistance with +100 points e.g. giving the chance of (spell mastery - spell resistance = chance to succeed). Some monsters have 120 in spell resistance.

I may be wrong and I cannot test this out today so if someone could test this, it could be clarified.

From Coreabilities.xml the following is written:

-<AbilityBonus InternalName="ImmuneToMagicAbility">

-<AbilityBonusOption InternalName="ImmuneToMagic">

<DisplayName>Immune to Magic</DisplayName>

<Description>Unit never fails a spell resistance check</Description>

<Icon>Ability_ImmuneToMagic_Icon.png</Icon>

-<GameModifier>

<ModType>Unit</ModType>

<Attribute>AdjustUnitStat</Attribute>

<StrVal>UnitStat_MagicResist</StrVal>

<Value>100</Value>

<Provides>Unit never fails a spell resistance check</Provides>

</GameModifier>

<CombatRating>50</CombatRating>

<HideWhenUpgraded>0</HideWhenUpgraded>

<IsCombatAbility>1</IsCombatAbility>

-<AIData AIPersonality="AI_General">

<AIPriority>5</AIPriority>

</AIData>

</AbilityBonusOption>

</AbilityBonus>

 

Immune to magic means that the unit gets additional 100 points to spell resistance.

Except you can cast spells or abilities on them if you have high enough spell mastery and get lucky with the resistance check.

As soon as you're above 100 spell mastery you can hit them.

this is bound to be confusing "Immune" means no spell works, whatever your level, shouldn't be calculated, should be a on/off switch