Magic resistance

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Null Field icon.png

Magic resistance is an attribute that reduces magical damage the unit receives. It acts as a counter part to armor, which grants physical damage resistance. All heroes have magic resistance, while most non-hero units have not. On heroes, unlike armor, magic resistance does not scale with levels, unless they are intelligene heroes, gain 0.15% resistance per point of intelligence. There are many abilities and items which can boost or reduce a unit's magical armor.

Magical damage[edit]

Main article: Damage types#Magical

Magical damage is a type of damage caused mostly by abilities. Unlike physical damage, it is not affected by armor. However, it is affected by magic resistance dealing more or less damage, depending on the unit's current magic resistance. Besides magic resistance, magical damage, just like physical and pure damage, is also affected by damage manipulation.

Mechanics[edit]

Magic resistance affects magical damage exclusively. It does not matter whether it is spell damage or attack damage, as long as it is magical, it is reduced. Even if magical damage has the HP Removal flag, it still is affected by magic resistance and reduced accordingly.

Stacking[edit]

All sources of magic resistance stack diminishingly. This means a unit's status resistance value changes less, the higher its status resistance is, and more, the lower it is. However, this does not mean a reduction in effectiveness with multiple sources. See the next section for details.

The magic resistance intelligence heroes gain through intelligence is all summed up into, and treated as one instance, which stacks diminishingly with other sourcers. This means with a theoretical intelligence of 667, an intelligence hero would have 100% magic resistance.

Formula

For total magic resistance of a unit (multiply the result by 100 to get the percentage value):

Total magic resistance = 1 − ((1 − natural resistance) × (1 - Intelligence × 0.15% on intelligence heroes) × (1 − first resistance bonus) × (1 − second resistance bonus) × (1 + first resistance reduction) × (1 + second resistance reduction))

For magical damage after magic resistance:

Actual damage = magical damage × (1 − natural resistance) × (1 - Intelligence × 0.15% on intelligence heroes) × (1 − first resistance bonus) × (1 − second resistance bonus) × (1 + first resistance reduction) × (1 + second resistance reduction)

Example:

Anti-Mage minimap icon.png Anti-Mage with level 4 Spell Shield icon.png Spell Shield and a Cloak icon.png Cloak has a magic resistance of:
1 - (1 - 0.25) × (1 - 0.5) × (1 - 0.15) = 68.125%
Visage minimap icon.png Visage on level 25 under the effect of Veil of Discord icon.png Veil of Discord and a level 4 Decrepify icon.png Decrepify cast by an enemy has a magic resistance of:
1 - (1 - 0.1) × (1 - (84 × 0.15)) × (1 + 0.25) × (1 + 0.6) = -57.32%

With a theoretical intelligence of 667, magic damage is fully negated on intelligence heroes. There are several abilities which grant 100% magic resistance. Because of the stacking rules, these abilities prevent a unit's magic resistance to be reduced or increased, as the formula will always result in 100%, no matter how big the magic resistance bonus or reduction.

Effective HP[edit]

Despite each source of magic resistance increasing the magic resistance value less the higher it is and making them seem less effective, each sources increases the unit's effective HP against magical damage by their base value. Effective HP means, how much damage can a unit take before dying, after reductions. In this case, magic resistance increases a unit's effective HP against magical damage. A unit with 0% magic resistance has 100% effective HP against magical damage, means magical damage equaling 100% of its health is required to kill it. Most heroes have 25% magic resistance by default, making their effective HP against magical damage 133.33%.

Formula:

Effective HP = Total HP / (1 - magic resistance)

Instead of 'diminishing' in effectiveness, multiple sources of resistance are actually more effective stacked than they are individually. Two sources of 25% resistance stacked provides 78% extra EHP whereas one source provides 33%.

Example:

Anti-Mage has 1260 health at max level. With his basic magic resistance, max level Spell Shield and a Cloak, he has an effective HP of:
1260 / (1 - 68.125 × 0.01) = 3952.94 effective HP
Visage has 1920 health at max level. With his basic magic resistance, while under the effect of Veil of Discord and an enemy level 4 Decrepify, he has an effective HP of:
1920 / (1 - -80 × 0.01) = 1066.67 effective HP

Magic resistance on units[edit]

Unit Base magic resistance Cloak Aura (Centaur Courser) icon.png Cloak Aura Pipe of Insight (3150) (Aura) Cloak (550)Glimmer Cape (1850) Hood of Defiance (1700) Pipe of Insight (3150) (Item + Aura) Glimmer Cape (1850) (Ability)
Standard hero 25% 32.5% 32.5% 36.25% 43.75% 52.75% 64.94% / 58.75%
Visage minimap icon.png Visage 10% 19% 19% 23.5% 32.5% 43.3% 57.93% / 50.5%
Pudge minimap icon.png Pudge (level 4 Flesh Heap icon.png Flesh Heap) 34% 40.6% 40.6% 43.9% 50.5% 58.42% 69.15% / 63.7%
Rubick minimap icon.png Rubick (level 4 Null Field icon.png Null Field) 41.5% 47.35% 47.35% 50.28% 56.13% 63.15% 72.65% / 67.83%
Viper minimap icon.png Viper (level 4 Corrosive Skin icon.png Corrosive Skin) 43.75% 49.38% 49.38% 52.19% 57.81% 64.56% 73.7% / 69.06%
Anti-Mage minimap icon.png Anti-Mage (level 4 Spell Shield icon.png Spell Shield) 62.5% 66.25% 66.25% 68.13% 71.88% 76.38% 82.47% / 79.38%
Huskar minimap icon.png Huskar (level 4 Berserker's Blood icon.png Berserker's Blood) 62.5% 66.25% 66.25% 68.13% 71.88% 76.38% 82.47% / 79.38%
Lone Druid Spirit Bear icon.png Spirit Bear (level 4) 33% 39.7% 39.7% 43.05% 49.75% 57.79% 68.68% / 63.15%
Warlock Golem icon.png Warlock's Golem 33% 39.7% 39.7% - - - 63.15%
Visage Familiar icon.png Familiars 35% 41.5% 41.5% - - - 64.25%
Necronomicon 1 icon.png Necronomicon summons 40% 52% 46% - - - -
Broodmother Spiderling icon.png Spiderlings, Broodmother Spiderling icon.png Spiderites, Enigma Eidolon icon.png Eidolons, Mud Golem icon.png Mud Golems & Mud Golem icon.png Shard Golems 50% 60% 55% - - - -
Roshan icon.png Roshan 55% 64% 59.5% - - - -
Ancient creeps 70% 76% 73% - - - -
Siege creeps & Lycan Wolf icon.png Lycan Wolves 80% 84% 82% - - - -

Sources of magic resistance bonus[edit]

  • Spell Shield icon.png
    Magic Resistance Bonus: 20%/30%/40%/50% (Talent 45%/55%/65%/75%)
    Passive.
  • Cloak Aura (Centaur Courser) icon.png
    Radius: 900
    Hero Magic Resistance Bonus: 10%
    Non-Hero Magic Resistance Bonus: 20%
    Multiple sources of Cloak Aura stack.
  • Cloak icon.png
    Magic Resistance Bonus: 15%
    Passive.
  • Glimmer Cape icon.png
    Magic Resistance Bonus: 15%
    Passive.
  • Glimmer Cape icon.png
    Magic Resistance Bonus: 45%
    Duration: 5
    Glimmer provides the magic resistance bonus only while invisible. Has a 0.6 seconds fade time and reapplies itself for the duration.
  • Hood of Defiance icon.png
    Magic Resistance Bonus: 25%
    Passive.
  • Berserker's Blood icon.png
    Max Magic Resistance Bonus: 20%/30%/40%/50%
    Passive. Grants magic resistance for each point of health missing, reaching the cap at 10% health.
  • Pipe of Insight icon.png
    Magic Resistance Bonus: 30%
    Passive.
  • Pipe of Insight icon.png
    Radius: 900
    Magic Resistance Bonus: 10%
  • Flesh Heap icon.png
    Magic Resistance Bonus: 6%/8%/10%/12%
    Passive.
  • Null Field icon.png
    Radius: 1200
    Magic Resistance Bonus: 10%/14%/18%/22% (Talent 15%/19%/23%/27%)
    Aura. When toggled to defensive mode.
  • Demolish (Spirit Bear) icon.png
    Magic Resistance Bonus: 33%
    Passive. Only available on level 4.
  • Corrosive Skin icon.png
    Magic Resistance Bonus: 10%/15%/20%/25%
    Passive.

Sources of magic resistance reduction[edit]

  • Ice Vortex icon.png
    Radius: 275
    Magic Resistance Reduction: 15%/20%/25%/30% (Talent 23%/28%/33%/38%)
    Vortex Duration: 16
    The effect lingers for 0.5 seconds.
  • Natural Order icon.png
    Radius: 350
    Base Magic Resistance Reduction: 40%/60%/80%/100%
    Only reduces base magic resistance, ignoring magic resistance bonuses. The aura's debuff lingers for 1 second.
  • Ethereal Blade icon.png
    Magic Resistance Reduction: 40%
    Enemy Duration: 3
    Ally Duration: 4
    Does not stack with the reductions of other ethereal effects, the one with higher value takes priority.
  • Ghost Scepter icon.png
    Magic Resistance Reduction: 40%
    Duration: 4
    Does not stack with the reductions of other ethereal effects, the one with higher value takes priority.
  • Ghost Shroud icon.png
    Magic Resistance Reduction: 30%
    Duration: 3/3.5/4/4.5
    Does not stack with the reductions of other ethereal effects, the one with higher value takes priority.
  • Decrepify icon.png
    Enemy Magic Resistance Reduction: 30%/40%/50%/60%
    Ally Magic Resistance Reduction: 25%
    Duration: 3.5
    Does not stack with the reductions of other ethereal effects, the one with higher value takes priority.
  • Null Field icon.png
    Radius: 1200
    Enemy Magic Resistance Reduction: 10%/14%/18%/22% (Talent 15%/19%/23%/27%)
    When toggled to offensive mode. The aura's debuff lingers for 0.5 seconds.
  • Ancient Seal icon.png
    Magic Resistance Reduction: 30%/35%/40%/45% (Talent 45%/50%/55%/60%)
    Duration: 3/4/5/6
  • Veil of Discord icon.png
    Radius: 600
    Magic Resistance Reduction: 25%
    Duration: 16
  • Nethertoxin icon.png
    Radius: 300
    Enemy Magic Resistance Reduction: 10%/15%/20%/25%
    Duration: 8

Sources of 100% magic resistance[edit]

These abilities grant 100% magic resistance to the affected units, reducing every magical damage they take to 0, and ceasing the effects of magic resistance reductions.

Magical damage barrier[edit]

Magical damage barriers absorb a set amount of magical damage, no matter whether they come from spells (magical spell damage) or attacks (magical attack damage). They absorb the damage before it is reduced by magic resistance, unless the resistance is provided by spell immunity. This means when a hero with for example 25% magic resistance and a 300 health damage barrier gets hit by 400 magical damage, the shield will absorb 300 of that. The exceeding 100 are not absorbed and are now reduced by the 25% magic resistance down to 75. So in this scenario, the hero takes 75 damage. This means a barrier is more effective the lower a unit's magic resistance is, similar to how damage block is more effective, the lower the armor is.

Multiple sources of magical damage barriers do not stack. When affected by multiple, all of them deplete at the same time. For example, if a unit is affected by a level 4 Flame Guard (500 barrier health) and by Pipe of Insight (400 barrier health), and then takes 300 magical damage, both shields lose 300 capacity, leaving Flame Guard with 200 and Pipe of Insight 100 absorb capacity.

Sources of magic damage barriers[edit]

See also[edit]