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Counterspell icon.png

▶️ Thy magic harms me not.
Anti-Mage

Magic Resistance is a stat that reduces (or increases, if negative) magical damage a unit takes from spells and magic attacks. Every unit is capable of gaining or losing magic resistance, and most units start with a small amount of base resistance. A hero's magic resistance can be passively increased with Talent talents, certain items, and some abilities. Magic resistance of any unit can also be temporarily increased or reduced with some abilities.

Total magic resistance is defined as

Magic Resistance = 1 - (1 - Base Magic Resistance) × (1 - Magic Resistance Modifiers i )

Base Magic Resistance[]

Base Magic Resistance is a value that never changes throughout a game. It consists of one fixed value set for each unit individually. The base magic resistance of a unit can be a negative number.

Heroes

All 123 heroes currently have the same Base Magic Resistance value: 25%

Creeps[]

Units Magic resistance
Mega Melee Creep, Mega Ranged Creep, Melee Creep, Ranged Creep, Super Melee Creep, Super Ranged Creep 0%
Lycan Lane Wolf 70%
Siege Creep, Super Siege Creep 80%

Summons[]

Summons Magic resistance
Astral Spirit, Earth, Fire, Spirit Bear 0%
Void 20%
Storm 25%
Warlock Golem 33%
Familiar 35%

Base Magic Resistance Negation[]

Some abilities negate or ignores a unit's base magic resistance by removing a percentage of the base magic resistance on the target. This magic resistance negation only affects the base magic resistance value of units, other sources of magic resistance are not affected.

Natural Order (and Unknown Unit icon.png Astral Spirit's Natural Order) interact with magic resistance differently. Instead of stacking multiplicatively with other sources of magic resistance, it acts as a multiplier for the base magic resistance. These two abilities are currently the only two sources of base magic resistance negation, and it is defined as

This means, for heroes with 25% base magic resistance, Natural Order reduces magic resistance by 10%/15%/20%/25%, down to 15%/10%/5%/0%.

Base Magic Resistance Negation Sources
  • Natural Order icon.png
    Radius: 350
    Base Magic Resistance Reduction: 40%/60%/80%/100%
    While Unknown Unit icon.png Astral Spirit is not summoned, the spirit is hidden and periodically moved along with Elder Titan, so that effectively, it is centered around him.
  • Natural Order (Astral Spirit) icon.png
    Radius: 350
    Base Magic Resistance Reduction: 40%/60%/80%/100%
    The effects are provided by an aura, affects enemies within range of the Unknown Unit icon.png Astral Spirit. The reduction is based on the enemies' base magic resistance. The debuff lingers for 1 second.

Pure Damage[]

Main Articles: Damage Types and HP Removal

Pure Damage is a damage type that is not reduced by Armor or Magic Resistance. It is also not amplified by magical damage amplification abilities, fully ignores Armor and Damage Block. It does not affect invulnerable units.

There are a few sources that can manipulate Pure Damage, with Dispersion being one of them. This mechanic is called damage reduction. Pure damage affects units with Spell Immunity (because spell immunity does not block damage), but that does not mean that an ability that deals pure damage is able to target spell immune units.

Total Magic Damage[]

Calculating the total magic damage of an ability involves using a few multipliers, Magic Resistance Multiplier, Actual Base Magic Resistance, Magic Damage Barrier and Magic Damage Negation Sources (if any). The total or actual magic damage dealt is equal to how much health a target immediately loses as a direct result.

Actual magic damage dealt after magic resistance is defined as

Magic Damage Dealt = (Magical Damage - Magic Damage Barrier - Magic Damage Negations) × (1 - Magic Resistance)

Magic Damage Barrier absorbs a set amount of magic damage before it is reduced by magic resistance.

Magic Resistance Stacking[]

Multiple sources of magic resistance stack multiplicatively. This means a unit's magic resistance value changes less the higher its magic resistance is, and more the lower it is. This prevents a unit from reaching 100% magic resistance by stacking different sources up. All sources of magic resistance modification stack fully with the exception of Ethereal buffs and debuffs.

Total magic resistance is defined as

Magic Resistance = 1 - (1 - Base Magic Resistance) × (1 - Magic Resistance Modifiers i )

However, there are a few abilities that directly sets a unit's magic resistance to 100%, e.g. Fate's Edict.

Example 1
Anti-Mage minimap icon.png Anti-Mage have Level 4 Counterspell and a Cloak icon.png Cloak. What is his current magic resistance?
Base hero magic resistance: 0.25
Bonus magic resistance: Counterspell: 0.45, Cloak icon.png Cloak: 0.15
Magic resistance reduction: 0 (None)
Total Magic Resistance
= 1 - ((1 - 0.25) × (1 - 0.45) × (1 - 0.15))
= 64.94%
Anti-Mage minimap icon.png Anti-Mage's current magic resistance in this example is 64.94%.
Example 2
Visage minimap icon.png Visage is at max level under the effect of a Level 4 Ancient Seal and a Level 4 Decrepify. What is his current magic resistance?
Base hero magic resistance: 0.25
Bonus magic resistance: 0 (None)
Magic resistance reduction: Ancient Seal: -0.35, Decrepify: -0.6
Total Magic Resistance
= 1 - ((1 - 0.25) × (1 + 0.35) × (1 + 0.6))
= -62%
Visage minimap icon.png Visage's current magic resistance in this example is -62%. Magic resistance reduction's calculation is highlighted red in this example.

Magical Damage Barrier[]

Magical damage barriers absorb a flat amount of magical damage, no matter whether it comes from abilities (magical spell damage) or attacks (magical attack damage). The barrier absorbs the damage before it is reduced by magic resistance, and it is defined as the formula above.

Example
Anti-Mage minimap icon.png Anti-Mage has a 300 health damage barrier, and gets hit by 400 magical damage. How much actual magical damage will he take?
Base magic resistance: 0.25
Magical Damage Taken
= (400 - 300) × (1 - 0.25)
= 75
Anti-Mage minimap icon.png Anti-Mage will take 75 magical damage in this example.

This means the exceeding 100 magical damage is not absorbed and the damage is reduced by Anti-Mage's base 25% magic resistance to 75 magical damage. In this example, Anti-Mage minimap icon.png Anti-Mage takes 75 magic 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.

Magical Damage Barrier Stacking[]

Multiple sources of magical damage barriers work independently and do not stack. When a unit is affected by multiple magical damage barriers, all of them deplete at the same time.

However, if a unit is affected by multiple barriers receive a damage instance that is greater than all barriers individually, the damage gets blocked as if the barriers were one barrier with combined capacity.

Magical Damage Barrier stacking is defined as

Magical Damage Barrier =

With x being the incoming magical damage value, B the source(s) of the magical damage barrier value.

Example 1
Ember Spirit minimap icon.png Ember Spirit is affected by Level 4 Flame Guard and Barrier of Pipe of Insight. He then takes 250 magical damage. Both magical damage barriers will lose 250 capacity.
Barrier capacity: Flame Guard: 400, Barrier: 400
Since the incoming magical damage is less than B1 and B2:
B1 ( Flame Guard)
= 400 - 250
= 150
B2 ( Barrier)
= 400 - 250
= 150
Since incoming magical damage is less than all individual barriers. Both Flame Guard and Barrier will now have 150 and 150 remaining magic barrier capacity respectively in this example.
Example 2
Ember Spirit minimap icon.png Ember Spirit is affected by Level 4 Flame Guard and Barrier of Pipe of Insight. He then takes 1000 magical damage.
Barrier capacity: Flame Guard: 400, Barrier: 400
Since the incoming magical damage is more than B1 and B2 combined:
Incoming Magical Damage
= 1000 - (400 + 400)
= 200
Since incoming magical damage is greater than the sum of both barriers, both Flame Guard and Barrier are depleted, and magical damage is blocked as if the barriers were one barrier with combined capacity, highlighted in blue in this example. Ember Spirit minimap icon.png Ember Spirit takes the remaining 200 damage before applying magic resistance.

Magical Damage Barrier Sources[]

Effective HP[]

The total amount of magic damage a unit can take due to magic resistance is known as effective HP (or EHP). 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 magic damage by their base value.

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. All 123 have 25% magic resistance by default, making their effective HP against magical damage 133.33%.

Magic Resistance -100% -75% -50% -25% 0% 25% 50% 75% 100%
Effective HP 500 571 667 800 1000 1333 2000 4000

This definition of EHP assumes all damage taken is magic damage. EHP against physical damage (such as basic hero attacks etc.) is modified by armor.

Effective HP against magical damage is defined as


EHP = Σ CurrentHP / (1 - Σ 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 77.78%, extra EHP whereas one source provides 33.33%.

Examples[]

Example 1
Anti-Mage minimap icon.png Anti-Mage at max level has 1540 health with Level 4 Counterspell and a Cloak icon.png Cloak, how much EHP against magical damage he has?
According to the previous example in magic resistance stacking above, Anti-Mage minimap icon.png Anti-Mage with Level 4 Counterspell and a Cloak icon.png Cloak has a magic resistance of 64.94% (or 0.6494).
Base magic resistance: 0.25
Bonus magic resistance: Counterspell: 0.45, Cloak icon.png Cloak: 0.15
EHPm
= 1540 / (1 - 0.649375)
= 4392.16
Anti-Mage minimap icon.png Anti-Mage has 4392.16 EHP against magical damage in this example.
Example 2
Visage minimap icon.png Visage has 2260 health at max level. While under the effect of a Level 4 Ancient Seal and Level 4 Decrepify, how much EHP against magical damage he has?
According to the previous example in magic resistance stacking above, Visage minimap icon.png Visage who is affected by those two abilities will have a magic resistance of -62% (or -0.62).
Base hero magic resistance: 0.25
Bonus magic resistance: 0 (None)
Magic resistance reduction: Ancient Seal: 0.35, Decrepify: 0.6
EHPm
= 2260 / (1 - (-0.62))
= 1395.06
Visage minimap icon.png Visage has 1395.06 EHP against magical damage in this example.

Modifying Magic Resistance[]

Several abilities and items have abilities that grant or reduce magic resistance.

Magic Resistance Increasing Sources[]

1 Requires Talent talent.
2a Requires Aghanim's Scepter icon.png Aghanim's Scepter.
2b Requires Aghanim's Shard icon.png Aghanim's Shard.

Talents[]

The following heroes have a Talent talent that grants them bonus magic resistance.

Bonus Level 10 Level 15 Level 20 Level 25
Left Right Left Right Left Right Left Right
Magic Resistance
  • Bane minimap icon.png +12%
  • Death Prophet minimap icon.png +12%
  • Enchantress minimap icon.png +10%
  • Doom minimap icon.png +12%
  • Primal Beast minimap icon.png +12%
  • Vengeful Spirit minimap icon.png +12%
  • Morphling minimap icon.png +15%
  • Techies minimap icon.png +20%
  • Elder Titan minimap icon.png +15%
  • Necrophos minimap icon.png +15%

With the 25% magic resistance and no other sources of magic resistance, the following heroes with bonus magic resistance talents effectively have their magic resistance increased up to:

Heroes Magic Resistance Talent Magic Resistance Total Increased Value
Basic Magic Resistance (25%)
Enchantress minimap icon.png +10% 32.5% +7.5%
Bane minimap icon.png Death Prophet minimap icon.png Doom minimap icon.png Primal Beast minimap icon.png Vengeful Spirit minimap icon.png +12% 34% +9%
Elder Titan minimap icon.png Morphling minimap icon.png Necrophos minimap icon.png +15% 36.25% +11.25%

Besides these, the following heroes have talents which increase the magic resistance of the units they summon

Specific Summons Magic Resistance Bonus

Items[]

These items grant bonus magic resistance to the hero who has them equipped.

Magic Resistance Granting Items
Item Value Item Cost Cost/Value Point
Arcanist's Armor icon.png Arcanist's Armor 20 N/A N/A
Bloodthorn icon.png Bloodthorn 20 6800 Gold 340 Gold
Cloak icon.png Cloak 15 500 Gold 33.33 Gold
Cloak of Flames icon.png Cloak of Flames 10 N/A N/A
Eternal Shroud icon.png Eternal Shroud 20 3300 Gold 165 Gold
Glimmer Cape icon.png Glimmer Cape 15 1950 Gold 130 Gold
Hood of Defiance icon.png Hood of Defiance 18 1500 Gold 83.33 Gold
Mage Slayer icon.png Mage Slayer 20 2400 Gold 120 Gold
Nether Shawl icon.png Nether Shawl 20 N/A N/A
Pipe of Insight icon.png Pipe of Insight 30 3475 Gold 115.83 Gold
Titan Sliver icon.png Titan Sliver 16 N/A N/A
Trickster Cloak icon.png Trickster Cloak 20 N/A N/A
Vambrace (Strength) icon.png Vambrace (Strength) 10 N/A N/A
Values may include portions from actives or auras.

Magic Resistance Reducing Sources[]

1 Requires Talent talent.
2a Requires Aghanim's Scepter icon.png Aghanim's Scepter.
2b Requires Aghanim's Shard icon.png Aghanim's Shard.

Ethereal[]

Main Article: Ethereal

Ethereal, sometimes referred to as ghost form, is a type of status effect that makes affected units immune to all physical damage, grants them attack immunity, while also disarming them. It also reduces their magic resistance, causing them to take additional magical damage. Affected units are able to control every other aspect of their character.

The magic resistance reduction of multiple ethereal effects does not stack, the one with higher value takes priority, and it is defined as

Eth = (1 - MAX Ethereal Magic Resistance Reduction)

Spell Immunity[]

Default buff icon
Error sound

Main Article: Spell Immunity

Spell immunity (formerly known as magic immunity) is a modifier which prevents most spells to target the affected unit. This includes single-targeted, area of effect, passive and active abilities. A unit having 100% magic resistance does not equal to being spell immune. Therefore, Spell Immunity and Magic Resistance are separate and different mechanics.

Version History[]

Version
Description

Patch History[]

Patch
Description
  • Fixed recasting magic damage barrier abilities not resetting the damage capacity of the magic barrier.
  • Update 2
    • Fixed magical damage amplification when a unit drops below 0% magic resistance.
  • Fixed magic resistance not stacking properly.
  • Fixed various magic resistance rules.
  • Fixed bugs with how magic resistance from base and items were calculated on illusions.


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