Debuff Immunity



Spell immunity (formerly known as magic immunity) is a modifier which prevents most spells to target the affected unit. This includes single-targeted spells, area spells, passive and active abilities.

Spell immunity may be the main part of a spell, but it also is used as an extra layer of protection by some abilities (usually combined with invulnerability).

Mechanics
Spell immunity is a status effect (also known as modifier). Most spells in the game first check wether or not the unit has the spell immunity modifier on. If the modifier is present, single target spells cannot target the unit at all, while area of effect spells ignore the unit and already ongoing effects may stop affecting it. However, some spells (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 is noted down in the description boxes of each ability, right below the ability name.

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 any delayed effect.

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

Damage interaction
All sources of spell immunity also set the affected unit's magic resistance to 100%. This leads to the affected unit taking no magical damage at all, not even from spells which pierce spell immunity. Their damage technically still hits the unit, but gets reduced to 0. This means they may still proc on-damage effects, since some of them do react on 0 damage instances as well.

Since magic resistance only affects magical damage, the unit is still fully affected by physical and pure damage. If a piercing ability uses one of those damage types, it does damage the unit.

If an ability does not pierce spell immunity, it also does not attempt to damage spell immune units, regardless of the damage type. In order for a spell 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.

Dispelling
Most sources of spell immunity also dispel the target upon getting applied, removing all buffs or debuffs a basic dispel can remove. The dispel applied by spell immunities is slightly stronger than a basic dispel and can remove a couple of more status effects. However, not all of them apply a dispel. A list of dispellable effects can be found here.

Since dispels only remove buffs off of enemies and debuffs off of allies, it is possible for units to turn spell immune without losing any buffs or debuffs (doable with Omniknight's ). In this case, most buffs/debuffs still apply their effects normally. Only a few of them are inactive while the unit is spell immune. This means that a damage-over time spell may still damage the unit. If it is magical damage, it gets reduced to 0, which is enough to proc some on-damage effects.

Sources of spell immunity
These abilities grant spell immunity as a main part of the spell. They all apply a special form of dispel upon cast which removes a few more status effects than a regular dispel.

These abilities also apply spell immunity. However, they only grant spell immunity as an extra layer of protection on top of the invulnerability they grant. This means their spell immunity only matters for spells which can affect invulnerable units (e.g. can target invulnerable units, but not spell immune units). These abilities do not apply the special spell immunity dispel like the above sources. However, some of them still do dispel, independent from the spell immunity.

With a very few exceptions, most non-hero units gain their permanent spell immunity through a passive ability.

Other units with spell immunity either gain it through a status buff, or do not have any indicator at all.

Spell immunity on allies
Every not-targeted spell, be it an area spell or a spell which affects self upon cast, pierces spell immunity for allies and self, with a very few exceptions listed below.

As for single-target spells, only a few do not pierce spell immunity, which are listed below as well.

1 These abilities cannot target spell immune allies. However, if an ally turns spell immune after cast, their effects continue to affect the unit.

2 Life Break, Rot and Double Edge do not attempt to apply the self-damage while spell immune.

3 Purge from Diffusal Blade and the Satyr Banisher cannot target spell immune allies, unless the ally is affected by.

4 Double Damage and Haste runes do not apply their buffs on spell immune units.

5 Although Ethereal Blade can be cast on spell immune allies or self and Ghost Scepter can be used while spell immune, they do not put spell immune units into ethereal form.

6 Astral Imprisonment and Phantom Strike cannot target spell immune allies or self. Their self-buff upon targeting enemies is applied while spell immune.

The following single-target abilities can target spell immune allies.

Note: Some of these abilities can be cast on allies and on enemies. However, only because they can target allies, it does not mean that they also can target enemies. They are listed again in the enemy section in their respective lists.

Spell immunity on enemies
Spells interact very differently when facing spell immune enemies. Most of them cannot affect spell immune units, some of them can only affect them partially, and some fully pierce spell immunity.

Fully piercing
These abilities fully affect spell immune units. This also goes for listed spells which only deal magical damage. In those cases, the spells attempt to damage the enemy, resulting in 0 damage instances, which may be enough to trigger some on-damage effects.

Besides the listed abilities, all Critical Strikes, Cleaves and Bashes (except 's Mini-Bash) pierce spell immunity.

Note: These lists do not consider spell immunity dispelling any buffs or debuffs. They only display how spells' effects react when combined with spell immunity.

These abilities also fully pierce spell immunity. However, unlike the ones above, these do not attempt to damage enemies, so no 0 damage instances are created.

1 Only the initial impact damage is fully blocked. Besides that, it fully pierces spell immunity.

2 The applied to enemies during Fiend's Grip (when upgraded) also pierces spell immunity.

3 Attempts to damage initially hit spell immune enemies. Spell immune enemies send echo waves towards nearby spell immune enemies. Echoes do not attempt to damage spell immune enemies.

Partially piercing
These abilities do not fully affect spell immune enemies, but are also not fully blocked. Usually, the main part of these abilities pierce spell immunity, while their secondary effects are blocked.

Not piercing
These abilities cannot apply their effects on spell immune units. Single Target abilities listed in here cannot target them all, while area effects ignore them. Debuffs which are placed before the target gets spell immune still continue to fully affect the target. In case of damaging debuffs, the damage is reduced to 0 if it is magical and may still trigger on-damage effects.

Note: As said before, these lists do not consider spell immunity dispelling any buffs or debuffs, since not all sources of spell immunity dispel. They only display how spells' effects react when combined with spell immunity.

1 These spells use projectiles. If their target turns spell immune while in flight, they have no effect on the target upon impact with the target. If they have an area effect, it is still applied to nearby enemies (except for ).

2 These abilities place a debuff on the target which deals damage. Since already placed debuffs still apply their effects on spell immune units, they also still deal damage. In case of magical damage, it gets reduced to 0.

3 These abilities have a delayed effect. Their delayed effect is not applied if their targets are spell immune at the time. This includes their damage.

4 These abilities have delayed effects as well. However, their effects are still fully applied, even when their target is spell immune at that time. This includes their damage.

5 These abilities continue to work when their target turns spell immune, applying the area effect. However, they do not affect spell immune enemies. This includes the primary target.

6 Unlike all other debuffs, these debuffs immediatly stop applying their effects to the target if it turns spell immune. They continue with their effects once the spell immunity is gone, given the debuffs did not expire by then.

7 These abilities periodically check for spell immunity on their targets and end immediatly if it gets detected.