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| Spell damage | Spell damage sources |
Spell damage is all damage which is not dealt by physical attacks Attack damage is the amount of damage a unit is dealing with an unmodified basic attack; the base values are different for every hero. The total attack damage of a unit is the sum of 
. This includes all spells which deal magical, physical or pure damage. Even the damage dealt by attack modifiers Attack modifiers are modifiers which apply an effect to a unit s basic attacks. These effects can widely vary, from healing, to damaging or even disabling effects. Most of these modifiers have their own rules. For 
counts as spell damage, as long as the effect deals its damage in a separate instance from the attack damage.
Magic spell damage is influenced by magic resistance Magic resistance is an attribute of heroes, similar to armor. Instead of reducing physical damage, it reduces magical damage. All heroes, except for Meepo and Visage, possess 25% magic resistance from their armor type. This 
, physical spell damage is influenced by armor Armor is an attribute shared by all units. Armor is used to determine the amount of damage reduction (or amplification if an armor value is negative) a unit takes from physical damage sources. Higher armor and pure damage is not affected by either. All three underlie damage manipulation There are several ways to affect the final value of a damage instance. Damage can be manipulated on both ends, from the dealing unit (outgoing damage) and the receiving unit (incoming damage). Armor and magic 
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Sources of spell damage
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Spell amplification
Spell damage can be directly amplified. Each point of 
Intelligence Intelligence is the attribute that grants mana, mana regeneration and spell damage amplification. For each point of intelligence a hero gets: 11 Mana 0.04 Mana regeneration 0.07% Spell damage Additionally, intelligence heroes also get 1 
increases a hero`s spell damage by 0.07%, which equates to 1% spell damage for every 14 points of intelligence. Spell damage amplification of multiple sources stacks additively. The amplification does not only affect spell damage dealt against enemies, it also causes damage afflicted to allies or the own unit to get amplified.
Currently there is no unit ability that directly amplifies spell damage, but a couple of heroes have perks in the talents tree.
- Ancient Apparition - Talent by Level 10 Left
Spell Amplification: 8% - Batrider - Talent by Level 15 RightSpell Amplification: 5%
- Centaur Warrunner - Talent by Level 20 RightSpell Amplification: 10%
- Death Prophet - Talent by Level 10 RightSpell Amplification: 5%
- Disruptor - Talent by Level 20 LeftSpell Amplification: 10%
- Earth Spirit - Talent by Level 20 RightSpell Amplification: 15%
- Ember Spirit - Talent by Level 10 RightSpell Amplification: 8%
- Gyrocopter - Talent by Level 10 RightSpell Amplification: 6%
- Jakiro - Talent by Level 10 LeftSpell Amplification: 8%
- Leshrac - Talent by Level 20 RightSpell Amplification: 5%
- Lina - Talent by Level 20 RightSpell Amplification: 6%
- Lion - Talent by Level 20 LeftSpell Amplification: 8%
- Magnus - Talent by Level 10 LeftSpell Amplification: 15%
- Mirana - Talent by Level 15 RightSpell Amplification: 5%
- Necrophos - Talent by Level 20 RightSpell Amplification: 5%
- Nyx Assassin - Talent by Level 10 RightSpell Amplification: 5%
- Ogre Magi - Talent by Level 25 RightSpell Amplification: 15%
- Outworld Devourer - Talent by Level 25 LeftSpell Amplification: 8%
- Phoenix - Talent by Level 20 LeftSpell Amplification: 8%
- Puck - Talent by Level 20 RightSpell Amplification: 10%
- Rubick - Talent by Level 20 LeftSpell Amplification: 8%
- Shadow Demon - Talent by Level 15 LeftSpell Amplification: 8%
- Shadow Fiend - Talent by Level 15 RightSpell Amplification: 6%
- Storm Spirit - Talent by Level 25 RightSpell Amplification: 10%
- Timbersaw - Talent by Level 20 RightSpell Amplification: 5%
- Tinker - Talent by Level 15 LeftSpell Amplification: 4%
- Underlord - Talent by Level 15 LeftSpell Amplification: 12%
- Visage - Talent by Level 25 RightSpell Amplification: 20%
- Windranger - Talent by Level 20 RightSpell Amplification: 15%
These items passively increase the owner`s spell damage amplification by merely having them equipped. They either grant a flat bonus, or bonus through intelligence.
Unaffected by amplification
There are certain cases of abilities that ignore spell amplification. It is important to note that those spells cannot spell lifesteal, too.
In general abilities related to health manipulation (instantly killing effect, health cost, delayed damage) and regular attacks (cleave, instant attacks) do not benefit from spell amplification. The exceptions to this rule are
