Spell Immunity



Spell immunity (formerly known as magic immunity) is a status which prevents most spells from targeting the affected unit. This includes single-targeted, area of effect, passive and active abilities.

Spell immunity is not provided by any ability, but appears on some units as an extra layer of protection, usually on ward-type units, or in combination with invulnerability.

Spell immunity always comes combined with debuff immunity, which nullifies the effects of already existing debuffs on the unit.

Mechanics
Spell immunity is a status effect (also known as modifier). Most abilities in the game first check whether or not the unit is spell immune. If true, single-target abilities cannot target the unit at all, while area of effect abilities ignore the unit and already ongoing effects may stop affecting it. However, some abilities (and most ultimates) pierce spell immunity and can fully target and affect spell immune units.

Usually, a spell either fully pierces spell immunity, or it is fully blocked. However, there are a few exceptions to this rule. Whether or not a spell pierces spell immunity can be viewed in the interactions list.

When a unit turns spell immune while a projectile from an ability is already flying towards it, the projectile has no effect upon impact if the spell it originates from does not pierce spell immunity. The same applies to most, but not all delayed effects.

Spell immunity does not prevent regular attacks of any units. However, some attack modifiers do get blocked, but not all of them. Generally, critical strike, cleave, lifesteal, and most bashes pierce spell immunity.

Damage Interaction
Spell immunity itself does not interact with damage at all. If an ability pierces spell immunity and has a damage component, its damage will still be applied normally, regardless of its damage type. Therefore, spell immunity only governs if an ability has any effect, not its damage types (nor its damage values).

A 0 damage instance is still registered and still may proc on-damage effect, unless it is flagged as HP Removal.

If an ability does not pierce spell immunity, it does not attempt to damage spell immune units either, regardless of the damage type. In order for an ability to damage spell immune units, it must be set to pierce spell immunity, or it must be already affecting it in case of buffs/debuffs.

Dispel
Certain modifiers periodically check for spell immunity and remove themselves if it is detected. The following abilities periodically check for spell immunity:

Debuff Immunity
Debuff immunity is an innate component of spell immunity, stopping the effects of already existing debuffs on the unit, allowing them to resume once the spell immunity and thus the debuff immunity expires.

Non-hero Units
The following units are permanently spell immune, either through a passive ability, or a modifier

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