Magic Resistance

“

▶️ 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 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 talents, certain items, and some abilities. Magic resistance of any unit can also be temporarily increased or reduced with some abilities.

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

Heroes	Magic resistance
	25%

Creeps

Units	Magic resistance
Mega Melee Creep, Mega Ranged Creep, Melee Creep, Ranged Creep, Super Melee Creep, Super Ranged Creep	0%
Flagbearer Creep, Mega Flagbearer Creep, Super Flagbearer Creep	40%
Lycan Lane Wolf	70%
Mega Siege Creep, Siege Creep, Super Siege Creep	80%

Summons

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

Stacking

All 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.

There are several abilities that set a unit's magic resistance to 100%.

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 − 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 − first resistance bonus) × (1 − second resistance bonus) × (1 + first resistance reduction) × (1 + second resistance reduction)

Base magic resistance negation

Natural Order interacts with magic resistance differently. Instead of stacking manipulatively with other sources of magic resistance, it acts as a multiplier for the base magic resistance. Natural Order is currently the only source of base magic resistance negation.

Example:

Anti-Mage with level 4 Counterspell and a Cloak has a magic resistance of:

1 - (1 - 0.25) × (1 - 0.45) × (1 - 0.2) = 67%

Visage on max level under the effect of a level 4 Ancient Seal and a level 4 Decrepify cast by an enemy has a magic resistance of:

1 - (1 - 0.25) × (1 + ) × (1 + 0.6) = %

Effective HP

The extra damage a unit can take due to magic resistance is known as its extra effective HP (or EHP) for magical damage. 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. 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 0.25 magic resistance by default, making their effective HP against magical damage 133.33%.

Magic resistance	-100%	-75%	-50%	-25%	-10%	0%	10%	25%	50%	75%	100%
Effective HP	500	571	667	800	909	1000	1111	1333	2000	4000	∞

Calculating effective HP

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 effective HP whereas one source provides 33%.

Example

Anti-Mage has 1550 health at max level. With his basic magic resistance, max level Counterspell and a Cloak, he has an effective HP of:

1550 / (1 - 67 × 0.01) = 4696.97 effective HP

Visage has 2122 health at max level. With his basic magic resistance, while under the effect of a level 4 Ancient Seal and an enemy level 4 Decrepify, he has an effective HP of:

2122 / (1 - × 0.01) = effective HP

Modifying magic resistance

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

Magic resistance increasing abilities

The following abilities increase magic resistance:

Magic resistance increasing abilities

• Anti-Mage - Counterspell
  
  Magic resistance bonus: 15%/25%/35%/45% ( 35%/45%/55%/65%)
  Passive.
• Centaur Courser - Cloak Aura
  
  Hero magic resistance bonus: 1200
  Non-hero magic resistance bonus: 10%/12%/14%/16%
  Aura, affects nearby allies. The buff lingers for 20%/24%/28%/32% seconds.
• Chaos Knight - Phantasm
  
  Illusion magic resistance bonus:
  The spawned illusions gain bonus magic resistance.
• Crystal Maiden - Arcane Aura
  
  Magic resistance bonus: 0.4/0.6/0.8/1 ( )
  Self bonus factor: 3
  Requires a Talent. Aura, affects all allies on the map. Has stronger effect on self. The buff lingers for 7 seconds.
• Dragon Knight - Elder Dragon Form
  
  Magic resistance bonus: 0%/0%/0%/20% ( )
  Only granted on level 4, which requires Aghanim's Scepter.
• Glimmer Cape - Glimmer
  
  Magic resistance bonus: 40
  Duration: 5
  Affects the target ally. The magic resistance is only applied when fully invisible. It is not applied during the fade time.
• Hellbear - [[Hellbear#|]]
  64px|text-top|link=Hellbear#
  Hero magic resistance bonus:
  Non-hero magic resistance bonus:
  Aura, affects nearby allies The buff lingers for seconds.
• Oracle - Fate's Edict
  
  Magic resistance bonus: 100%
  Duration: 3.5/4/4.5/5
  Affects the target unit.
• Pipe of Insight - Insight Aura
  
  Magic resistance bonus: 10%
  Aura, affects nearby allies. The buff lingers for 0.5 seconds.
• Pudge - Flesh Heap
  
  Magic resistance bonus: 1
  Passive.
• Spirit Bear - Demolish
  
  Magic resistance bonus: 33%
  Passive.
• Viper - Corrosive Skin
  
  Magic resistance bonus: 10%/15%/20%/25% ( 25%/30%/35%/40%)
  Passive.

Magic resistance reducing abilities

The following abilities reduce magic resistance:

Magic resistance reducing abilities

• Ancient Apparition - Ice Vortex
  
  Magic resistance reduction: 12/18/24/30 ( )
  Duration: 16%/19%/22%/25%
  Aura, affects enemies within the target area. The debuff lingers for 16%/19%/22%/25% seconds.
• Bane - Enfeeble
  
  Magic resistance reduction: 12/18/24/30
  Duration: 55%/60%/65%/70%
  Affects the target of every single-target non-item spell cast by the hero. The debuff is placed before the triggering spell takes effect.
• Elder Titan - Natural Order
  
  Base magic resistance negation: 40%/60%/80%/100%
  Aura, affects enemies within range of the Astral Spirit. The reduction is based on the enemies' base magic resistance. The debuff lingers for 1 second.
• Ethereal Blade - Ether Blast
  
  Magic resistance reduction: 80%
  Duration: 40%
  Affects the target unit. The magic resistance reduction of multiple ethereal effects does not stack, the one with higher value takes priority.
• Ghost Scepter - Ghost Form
  
  Magic resistance reduction: 40%
  Duration: 4
  Affects the caster. The magic resistance reduction of multiple ethereal effects does not stack, the one with higher value takes priority.
• Grove Bow - Magic Amp
  
  Magic resistance reduction: 15%
  Duration: 6
  Affects the attacked enemy.
• Necrophos - Ghost Shroud
  
  Magic resistance reduction: 1.45/1.55/1.65/1.75
  Duration: 0.5
  Affects the caster. The magic resistance reduction of multiple ethereal effects does not stack, the one with higher value takes priority.
• Pugna - Decrepify
  
  Ally magic resistance reduction: 10%/15%/20%/25%
  Enemy magic resistance reduction: 30%/40%/50%/60%
  Duration: 3.5 ( 4.5)
  Affects the target unit. The magic resistance reduction of multiple ethereal effects does not stack, the one with higher value takes priority.
• Skywrath Mage - Ancient Seal
  
  Magic resistance reduction: 3/4/5/6 ( )
  Duration:
  Affects the target enemy.
• Viper - Poison Attack
  
  Magic resistance reduction per stack: 4/8/12/16
  Max stacks: 3%/6%/9%/12%
  Duration: 4%/6%/8%/10%
  Affects the attacked enemy.

Magic resistance granting talents

The following heroes have a 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	+12%	+15% +20%				+20%	+25%

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

Specific summons magic resistance bonus

• Warlock - Talent by Level 25 Left
  
  s:value% Magic Resistance for Chaotic Offering Golems:
  

Magic resistance granting items

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

Magical damage barrier

Magical damage barriers absorb a set amount of magical damage, no matter whether it comes from spells (magical spell damage) or attacks (magical attack damage). They absorb the damage before it is reduced by magic resistance. 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 ( barrier health) and by Pipe of Insight (450 barrier health), and then takes 300 magical damage, both shields lose 300 capacity, leaving Flame Guard with -300 and Pipe of Insight 150 absorb capacity.
However, if a unit is affected by multiple barriers, and then receives a damage instance that is greater than all barriers individually, the damage gets blocked as if the barriers were one barrier with combined capacity. For example, if a unit is affected by a level 4 Flame Guard ( barrier health) and by Pipe of Insight (450 barrier health), and then takes 1000 magical damage, both barriers get depleted, and the unit takes the remaining 550 damage.

Sources of magic damage barriers

• Ember Spirit - Flame Guard
  
  Barrier Health: 70% ( )
  Duration: 60/135/210/285
  
• Hood of Defiance - Barrier
  
  Barrier Health: 350
  Duration: 12
  This is an old ability.
• Pipe of Insight - Barrier
  
  Barrier Health: 450
  Duration: 12
  Affects allies and structures within a 1200 radius on cast.

Mechanics Main Heroes Unit Type (Heroes / Clones / Illusions) Complexity Attributes Table Buyback Level Roles Gold Experience Animations Stats Armor Attributes ( Strength / Agility / Intelligence) / Universal) Health & Mana (HP Regen & MP Regen) Magic Resistance Movement Speed / Slow Resistance Status Resistance Turn Rate Misc Creep Controling Death / Denying Vision Unit Size (Collision Size / Bound Radius / Selection Box / Model Size) Gib Type / Shades Adjectives Buildings Towers / Barracks / Ancient / Fountain Effigy Neutral Buildings (Outposts / Watchers / Twin Gates / Lotus Pools) Abilities Type Active / Passive / Autocast Aura Accuracy / Evasion Channeling Damage Barrier Damage Block Damage Manipulation Damage Over Time Talents Teleport Targeting Area No Target Point Unit Vector Combinations Casting Cast Range / Motion Buffer Cast Animation (Cast Point + Backswing) Cooldown Reduction (Flat / Current Flat / Percentage) Reset Charge-based Runes Bounty Rune Water Rune Wisdom Rune Power Runes ( Amplify Damage Rune / Arcane Rune / Haste Rune / Illusion Rune / Invisibility Rune / Regeneration Rune / Shield Rune) Misc Random Distribution Transformation Attack Damage Attack Damage Instant Attack Heroes Attack Classes Attack Range (Acquisition Range) Attack Speed (BAT / Interval) Damage Types (Physical / Magical / Pure / Instant Kill) Flags (HP Removal / No-reflection / No-Spell-Lifesteal / No-Spell-Amplification) Projectile Speed Spell Damage (Outgoing / Incoming) Modifiers Bash Cleave / Splash Corruption Critical Strike Lifesteal / Spell Lifesteal Mana Break On-hit Effects Misc Damage Instance Animation / Orb Walking Status Effects Disables Cyclone Disabling Orders Forced Movement (Knockback) / Upward Movement Fear (Hypnosis) Hide Hex Root Leash Stun Sleep Taunt Movement Move Speed Slow Flying Movement Phased / Tree Walk / Unobstructed Movement Other Attack Immune / Non-targetable Attack Speed Slow Debuff Immunity Spell Immunity Invulnerability Invisibility Blind Break Disarm Ethereal Silence Mute Trap Dispels Basic Strong Death Items Mechanics Courier Sharing / Selling Disassemble Recipes Neutral Item Drop