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 resistance are the most common damage manipulators, affecting incoming physical and magical damage respectively (no similar trait exists for pure damage). They usually reduce damage, but can also amplify it if their values are negative. Spell damage amplification is the main trait for amplifying (but not for reducing) outgoing spell damage (no similar trait exists for attack damage). Besides these, there are some other ways to manipulate damage, ranging from amplifying damage, reducing damage and even negating damage completely.
Sources of damage manipulation
Amplifying incoming damage
Damage amplification causes afflicted units to take additional damage.
- Close Damage Amplification: 25%/30%/35%/40%
Far Damage Amplification: 12.5%/15%/17.5%/20%
Amplifies for half the value when the dealer and receiver are more than 2200 units apart from each other.
- Damage Amplification: 18%/24%/30%/36%
- Based on the ability the illusion is created by, it may take more damage than the hero it is based on.
- Max Damage Amplification: 20%/30%/40%/50%
Amplification gets spread evenly amongs all units debuffed on cast.
- Damage Amplification: 15%
- Max Damage Amplification: 20%/25%/30%
Min Damage Amplification: 1%
Max Radius: 200
Min Radius: 700
Amplification gets linearly stronger based on distance to Undying, reaching max amplification within a 200 radius.
Amplifying outgoing damage
Besides spell damage amplification, Bloodrage is the only ability able to amplify outgoing damage.
Reducing incoming damage
Just like how damage can be amplified, it can also be reduced.
- Rear Damage Reduction: 16%/24%/32%/40%
Side Damage Reduction: 8%/12%/16%/20%
Reduces damage for Bristleback when taking damage from his rear or sides.
- Damage Reduction: 25%
Illusion Damage Reduction: 75%
Reduces damage from all sources (more from illusions) while under Backdoor Protection. Also reduces damage from illusions by 50% while not protected.
- Based on the ability the illusion is created by, it may take less damage than the hero it is based on.
- Damage Reduction: 5%/10%/15%/20%
Reduces damage for Io and a Tethered ally.
- Damage Reduction: 40%/45%/50%
Reduces damage for all buffed allies, making them take that portion of damage later.
- Damage Reduction: 60%
Damage Absorbed per Mana: 1.6/1.9/2.2/2.5
- Damage Reduction: 40%
- Damage Reduction: 10%/14%/18%/22%
- Damage Reduction: 80%
- Max Layers: 4
Damage Reduction per Layer: 8%/12%/16%/20%
Layer Recharge Time: 6/5/4/3
Passive, loses 1 layer when taking player-based damage. Layers recharge after a short time. Also affects Visage's Familiars within range.
- Damage Reduction: 100%
Reduces damage for the frozen target and those cursed to attack their ally.
Reducing outgoing damage
These abilities are able to reduce outgoing damage.
Stacking damage reduction & amplification
Armor and magic resistance work separately from other damage manipulators. This means they always stack multiplicatively with any other listed ability.
Besides Borrowed Time's aura, Ghostship's rum and Mana Shield, all damage reducing and damage amplifying effects stack additively with each other. Borrowed Time, Ghostship and Mana Shield stack multiplicatively with them. Mana Shield also stacks multiplicatively with Borrowed Time and Ghostship. However, the damage reductions of Borrowed Time and Ghostship do not stack with each other, although both still react on the damage (Borrowed Time still heals Abaddon, and Ghostship's rum wear-off still counts the damage). The damage amplification which illusions usually have stacks multiplicatively with all other damage amplifying and reducing effects (considering they are able to affect illusions).
Examples of additive stacking (all values consider highest possible value, examples ignore armor and magic resistance, 100% is the base value):
100 + 40 + 50 - 20 = 170% damage
100 + 30 - 22 - 50 = 58% damage
100 - 80 - 20 = 0% damage
100 - 100 + 40 + 30 + 50 + 30 = 150% damage
Examples of multiplicative stacking:
(100 - 20 + 50) * 40% = 52% damage
- Medusa affected by the same as above, but also additionally by Ghostship takes:
(100 - 20 + 25) * 40% * 50% = 21% damage
(100 - 20 - 50) * 400% = 120% damage
Stacking outgoing damage manipulation stacks in the same way as incoming damage manipulation, i.e. additively. However, since incoming and outgoing manipulations happen at different times (outgoing happens first), they stack multiplicatively with each other.
Damage negation causes entire instances of damage to deal no damage to its target, however, the instance is still registered. This means, if something reacts on damage without having a minimum damage threshold, it still reacts on the negated damage.
- Negated Damage: 120
Can only negate magical damage. Can only negate a certain amount of damage per charge. Goes on cooldown upon negating an instance. Ignores damage lower than 50.
- Duration: 2.25
Can only negate 1 instance of damage from each player.
- Duration: 4
Can only negate physical damage.
Preventing on-damage effects
Many abilities react on damage a unit receives. In some cases, fully negating the damage causes them to not proc. However some on-damage effects also react on 0 damage so they still may proc even when the proccing damage got negated.
The following abilities and effects do not react on damage when it gets fully negated (reduced to 0):
- Aegis of the Immortal – Expire Restore
- Ancient Black Dragon – Splash Attack2
- Blink Dagger – Blink
- Bloodthorn – Soul Rend
- Bottle – Regenerate
- Bristleback – Bristleback3
- Clarity – Regenerate Mana
- Dazzle – Shallow Grave4
- Healing Salve – Regenerate Health
- Heart of Tarrasque – Health Regeneration
- Lifesteal – All sources1 2
- Lifestealer – Open Wounds
- Mjollnir – Static Charge
- Monkey King – Tree Dance
- Octarine Core – Spell Lifesteal
- Orchid Malevolence – Soul Burn
- Pugna – Life Drain
- Regeneration Rune – Regeneration
- Templar Assassin – Psi Blades2
- Tidehunter – Kraken Shell3
- Treant Protector – Living Armor5
- Urn of Shadows – Soul Release
- Visage – Soul Assumption3
- Wraith King – Reincarnation (Wraith Delay)4
2 These work when the damage gets negated by Aphotic Shield.
3 These abilities have damage counters, which do not work when the damage gets negated.
5 Despite Living Armor not reacting on damage which was already blocked by another source of damage negation, it still loses a charge per damage instance when the other source of damage negation was Aphotic Shield.
The following abilities still do react on fully negated damage:
- Bane – Nightmare
- Batrider – Sticky Napalm
- Battle Fury – Cleave
- Blade Mail – Damage Return
- Broodmother – Spin Web
- Death Prophet – Exorcism
- Dragon Knight – Elder Dragon Form (splash damage)
- Elder Titan – Echo Stomp
- Keeper of the Light – Recall
- Kunkka – Tidebringer
- Lifestealer – Feast
- Lone Druid – Summon Spirit Bear
- Magnus – Empower1
- Spectre – Dispersion2
- Spirit Bear – Return
- Sven – Great Cleave
- Tiny – Grow (cleave damage)
- Viper – Corrosive Skin
- Warlock – Fatal Bonds2
1 Both cleave and splash damage from Empower react on fully negated damage.
Pre-Heal, just like regular damage negation, prevents a unit from dying. However, the way in which that is achieved is completely different. Instead of directly reducing or negating damage, this mechanic rather manipulates the health of the unit.
A pre-heal only activates when the unit is going to receive a damage instance which exceeds its current health. If that happens, the unit's current health gets increased equal to the amount of the incoming damage plus one, right before the damage hits. This causes the unit's health to land exactly at 1. This also works when an incoming damage instance is greater than the unit's maximum health. In this case, its maximum health gets increased as well and immediately reverted to default after the damage hits.
This means that technically, the incoming damage is not reduced at all. This is the reason why the abilities which use this mechanic do not prevent any on-damage effects from triggering, unlike regular damage negation.
The following abilities use this pre-heal mechanic: