Magic resistance
| “ | Play 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 strength (with strength heroes gaining more than other heroes), talents, certain items, and some abilities. Magic resistance of any unit can also be temporary increased or reduced with some abilities.
Each point of strength increases a hero's magic resistance by 0.08 if it is an agility or intelligence hero, and 0.1 if it is a strength hero.
Contents
Base magic resistance[edit]
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[edit]
Creeps[edit]
Summons[edit]
| Summons | Magic resistance |
|---|---|
| Astral Spirit, Boar, Earth, Fire, Forged Spirit, Greater Treant, Hawk, Skeleton Warrior, Spirit Bear, Storm, Treant | 0% |
| Undying Zombie, Warlock's Golem | 33% |
| Familiar | 35% |
| Necronomicon Archer, Necronomicon Warrior, Spiderite, Spiderling | 40% |
| Eidolon, Wraith King Skeleton | 50% |
| Lycan Wolf | 80% |
Stacking[edit]
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%. Besides them, the magic resistance granted by strength can theoretically reach 100% as well, since the bonus from strength gets summed up into, and treated as one instance. This means, theoretically, strength heroes can reach 100% magic resistance with 1000 strength, and other heroes with 1250 strength.
- 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 - strength × 0.08%) × (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 - strength × 0.08%) × (1 − first resistance bonus) × (1 − second resistance bonus) × (1 + first resistance reduction) × (1 + second resistance reduction)
Example:
- Anti-Mage with level 4 Counterspell and a Cloak has a magic resistance of:
- 1 - (1 - 0.25) × (1 - 0.45) × (1 - 0.15) = 64.9375%
- Visage on level 25 under the effect of Veil of Discord and a level 4 Decrepify cast by an enemy has a magic resistance of:
- 1 - (1 - 0.1) × (1 - (96 × 0.08)) × (1 + 0.25) × (1 + 0.6) = -66.176%
Effective HP[edit]
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 1172 health at max level. With his basic magic resistance, max level Counterspell and a Cloak, he has an effective HP of:
- 1172 / (1 - 64.9375 × 0.01) = 3342.6 effective HP
- Visage has 1928 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:
- 1928 / (1 - -80 × 0.01) = 1071.11 effective HP
Modifying magic resistance[edit]
Several abilites and items have abilities that grant or reduce magic resistance.
Magic resistance increasing abilities[edit]
Besides spell immunity, which always grants 100% magic resistance, the following abilities increase magic resistance:
Magic resistance bonus: 15%/25%/35%/45% (
40%/50%/60%/70%)
Passive.
Hero magic resistance bonus: 10%
Non-hero magic resistance bonus: 20%
Aura, affects nearby allies. Multiple instances fully stack. The buff lingers for 0.5 seconds.
Magic resistance bonus: 45%
Duration: 5
Affects the target ally. The magic resistance is only applied when fully invisible. It is not applied during the fade time.
Hero magic resistance bonus: 10%
Non-hero magic resistance bonus: 20%
Aura, affects nearby allies. Multiple instances fully stack. The buff lingers for 0.5 seconds.
Magic resistance: 100%
Duration: 3/3.5/4/4.5
Affects the target unit.- Pipe of Insight - [[Pipe of Insight#|]]
Magic resistance bonus: 10%
Aura, affects nearby allies. The buff lingers for 0.5 seconds. 
Magic resistance bonus: 33%
Passive.
Magic resistance bonus: 10%/15%/20%/25% ( 16%/21%/26%/31%)
Passive.
Magic resistance reducing abilities[edit]
The following abilities reduce magic resistance:
Magic resistance reduction: 15%/20%/25%/30% ( Lua error in Module:Calculate at line 35: Unexpected < operator in expression "( 15/100+Lua error in Module:Show at line 24: attempt to index field '?' (a nil value)./100 )*100".)
Duration: 16
Aura, affects enemies within the target area. The debuff lingers for 0.5 seconds.
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 seconds.
Magic resistance reduction: 40%
Ally duration: 4
Enemy duration: 3
Affects the target unit. The magic resistance reduction of multiple ethereal effects does not stack, the one with higher value takes priority.
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.
Magic resistance reduction: 40%
Duration: 3/3.5/4/4.5
Affects the caster. The magic resistance reduction of multiple ethereal effects does not stack, the one with higher value takes priority.
Enemy magic resistance reduction: 25%
Ally magic resistance reduction: 30%/40%/50%/60%
Duration: 3.5 ( 5.5)
Affects the target unit. The magic resistance reduction of multiple ethereal effects does not stack, the one with higher value takes priority.
Magic resistance reduction: 30%/35%/40%/45% ( 45%/50%/55%/60%)
Duration: 3/4/5/6
Affects the target enemy.- Veil of Discord - [[Veil of Discord#|]]
Magic resistance reduction: 25%
Duration: 16
Affects all enemies within the target area. 
Magic resistance reduction: 10%/15%/20%/25%
Duration: 8
Aura, affects enemies within the target area. The debuff lingers for 0.5 seconds.
Magic resistance granting talents[edit]
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 |
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|
|
|
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Magic resistance granting items[edit]
These items grant bonus magic resistance to the hero who has them equipped.
| Item | Value | Item cost | Cost per value point |
|---|---|---|---|
| Bracer | 6 | 515 | 85.83 |
| Cloak | 15 | 550 | 36.67 |
| Glimmer Cape | 15 | 1950 | 130 |
| Holy Locket | 15 | 2650 | 176.67 |
| Hood of Defiance | 25 | 1700 | 68 |
| Pipe of Insight | 30 | 3025 | 100.83 |
Magical damage barrier[edit]
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, 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]
Barrier Health: 80/220/360/500 ( 330/470/610/750)
Duration: 8/12/16/20
Barrier Health: 325
Duration: 12- Pipe of Insight - [[Pipe of Insight#|]]Barrier Health: 400
Duration: 12
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