Ability damage is one of the game's archetypal damage types, and is the damage type dealt by most abilities. Ability damage is the pre-requisite for applying ability effects, such as Rylai's Crystal Scepter item Rylai's Crystal Scepter and Spell vamp icon Spell Vamp. Dealing ability damage will also generate aggression from turrets but, by contrast to basic attack damage, does not trigger the Call For Help AI on minions.

Ability damage is never described as such in-game, instead being listed as physical, magic or true damage. However, those typings can be attributed other archetypal damage types (e.g. basic attack damage can be physical and magical, too) and so knowing whether or not an effect deals ability damage can be hard to intuit.

The basic rule is: all damage-dealing abilities, excluding attack effects, deal ability damage.

Below lists exceptions.

Non-Damaging Abilities

The following non-damaging effects actually deal 1 ability damage, inflicted as true damage. This is sufficient to trigger spell effects, such as Luden's Echo item Luden's Echo, although will not incur any noticable healing from Spell vamp icon Spell Vamp.

Non-Abilities

The following non-abilities will also trigger spell effects:

Items
Summoner Spells
Runes

Thess lists may be incomplete.

On-Hit Ability Damage

The following attack effects deal ability damage, meaning they will trigger ability effects. The triggering basic attack will still apply other attack effects.

Attack Effects

As of V7.22, the following abilities now apply both attack effects and spell effects.

Note that, however, the damage dealt by these abilities is not classified as ability damage, except in the case of Whiplash Whiplash and the magic damage portion of Urchin Strike Urchin Strike. Except in those cases, the damage dealt by these abilities will not benefit from Spell vamp icon Spell Vamp. It is possible—as with Non-Damaging Abilities (above)—that these abilities actually deal 1 ability damage.

Probable Bug: Steel Tempest Steel Tempest is only triggering ability effects on the second and third cast in Steel Tempest's chain, and they are only applied to the first target hit.

Trivia

 v · e
Gameplay Elements