Immunity¶

Immunity in GAS means blocking the application of other Gameplay Effects. When an actor has an active effect with immunity configured, incoming effects that match the immunity criteria are rejected before they ever apply. The incoming effect is simply denied — it never enters the Active GE Container, never modifies attributes, never grants tags.

UImmunityGameplayEffectComponent¶

Immunity is configured through the UImmunityGameplayEffectComponent. You add this component to a GE, configure the immunity queries, and as long as that GE is active on the target, the target is immune to matching effects.

UCLASS(DisplayName="Immunity to Other Effects", MinimalAPI)
class UImmunityGameplayEffectComponent : public UGameplayEffectComponent
{
    // ...
public:
    /** Grants immunity to GameplayEffects that match this query. */
    UPROPERTY(EditDefaultsOnly, BlueprintReadOnly, Category = None)
    TArray<FGameplayEffectQuery> ImmunityQueries;
};

How It Works¶

When the GE with this component is added to the Active GE Container, the component registers a global callback on the ASC via OnActiveGameplayEffectAdded. From that point on, every incoming FGameplayEffectSpec is checked against the ImmunityQueries. If any query matches the incoming spec, the application is blocked.

The check happens in AllowGameplayEffectApplication, which is called during the application pipeline — before the effect would be added or executed.

FGameplayEffectQuery¶

The queries use FGameplayEffectQuery, which is a powerful matching struct. You can match on:

All conditions within a single query are ANDed — every specified field must match for the query to match. The ImmunityQueries array is ORed — if any query matches, immunity blocks the effect.

The ImmunityTrigger Delegate¶

When an effect is blocked by immunity, the OnImmunityBlockGameplayEffectDelegate on the ASC fires. This lets you react to blocked effects — for example, to play a "immune!" visual effect or log that something was blocked.

// Somewhere in your setup
ASC->OnImmunityBlockGameplayEffectDelegate.AddUObject(
    this, &AMyCharacter::OnImmunityTriggered);

// Your handler
void AMyCharacter::OnImmunityTriggered(
    const FGameplayEffectSpec& BlockedSpec,
    const FActiveGameplayEffect* ImmunityGE)
{
    // Play "immune" gameplay cue, show floating text, etc.
    UE_LOG(LogGame, Log, TEXT("Blocked effect: %s"),
        *BlockedSpec.Def->GetName());
}

This is purely informational — by the time the delegate fires, the incoming effect has already been rejected.

Practical Patterns¶

Invulnerability Frames (I-Frames)¶

A dodge roll grants brief total immunity to all damage:

GE_DodgeIFrames (Duration = 0.3s):

• Component: UImmunityGameplayEffectComponent
  • Query: EffectTagQuery matches any effect with tag Damage

During the 0.3s window, all incoming effects tagged Damage are blocked. Other effects (buffs, debuffs unrelated to damage) still apply.

Elemental Immunity¶

A fire resistance potion grants immunity to fire damage:

GE_FireResistancePotion (Duration = 30s):

• Component: UImmunityGameplayEffectComponent
  • Query: EffectTagQuery matches effects with tag Damage.Fire
• Component: UTargetTagsGameplayEffectComponent
  • Grants tag: Buff.FireResistance

Fire damage effects are blocked. Non-fire damage still applies. The granted tag can be used by other systems (UI showing "Fire Resistant", etc.).

CC Immunity After Stun¶

After a stun ends, grant a brief window of CC immunity:

GE_Stun (Duration = 2s):

• Component: UAdditionalEffectsGameplayEffectComponent
  • OnCompleteNormal: GE_CCImmunity

GE_CCImmunity (Duration = 3s):

• Component: UImmunityGameplayEffectComponent
  • Query: EffectTagQuery matches effects with tag CC
• Component: UTargetTagsGameplayEffectComponent
  • Grants tag: State.CCImmune

When the stun expires naturally, the immunity kicks in. If the stun is cleansed early (premature removal), you could choose not to grant the immunity by using OnCompleteNormal instead of OnCompleteAlways.

Immunity to Specific Sources¶

Block effects from a specific class:

• Query: EffectDefinition = UGE_PoisonDamage

Or block effects from a specific source object:

• Query: EffectSource = some specific actor or weapon

Stacking Immunity Considerations¶

If multiple active effects on a target each have immunity components, they all contribute. An incoming effect is blocked if any active immunity query matches it.

When an immunity-granting effect is removed, its immunity contribution is removed too. This is handled automatically by the component's callback cleanup.

Immunity vs. Other Rejection Mechanisms¶

There are several ways an effect can be prevented from applying. Here's how immunity compares:

The key distinction: immunity lives on the target's existing effects, while application requirements live on the incoming effect. Immunity says "I won't accept this." Application requirements say "I won't apply unless conditions are right."

Tips¶