Damage types

Damage is any means by which unit's current health can be reduced. Heroes, creeps, ancients, Roshan and fountains are all capable of dealing damage.

Damage sources
Damage can be dealt by attacks, abilities and items. Attack damage is the damage dealt per attack, and is displayed on the sword icon in the HUD. Heroes start off with a basic damage plus 1 extra damage per point of primary attribute. As heroes level up, they gain primary attributes and therefore gain damage. Items that grant increased "Damage" increase attack damage, and do not affect abilities and items. Abilities and items can also deal damage. These are generally fixed. However, some abilities can be upgraded with, while others scale with hero stats, conditions or enemy health etc.

Damage classification
All forms of damage in Dota 2 are classified by damage types. There are 3 primary damage types: Physical, Magical, and Pure. Physical Damage can be reduced by Physical Armor or Damage Block, Magical Damage can be reduced by Magical Damage Resistance, while Pure Damage cannot be reduced by either armor or magical damage resistance. All 3 primary damage types have some interaction with other damage-related game mechanics as noted in the table below. Damage may also have the HP Removal flag, causing the damage to ignore some mechanics which would manipulate it otherwise.

1 The only exceptions are and, whose damage is blocked.

2 These categories only count ability effects which directly manipulate damage, reducing, amplifying or completely blocking them, such as, and. They do not include abilities which amplify or reduce damage by increasing/reducing magic resistance/armor of units, such as, , and.

3 By itself, spell immunity does not interact with any damage type. All spells are rated as to whether or not they can pierce spell immunity independent of their damage type. Thus, spell immunity only governs if a spell has any effect, not how much damage it inflicts. To receive no effects from a spell, the spell must not pierce spell immunity and the target would require both spell immunity and 100% damage reduction of the damage type the spell inflicts. All sources of spell immunity also provide 100% magic resistance to the unit (similar to ), so a magical damage spell which pierces spell immunity, although technically still fully applying its damage, deals 0 damage to spell immune units, due to the 100% magic resistance it gains from spell immunity. A 0 damage instance is still registered and may proc on-damage effects. If a spell does not pierce spell immunity, then it also does not attempt to damage the target in the first place, so that no 0 damage instance occurs.

Physical
Physical damage can be inflicted by regular attacks from all units (including structures), and by certain abilities. Physical damage is modified by both armor and Damage Block, is unaffected by magic resistance, and cannot affect ethereal units. The abilities and  make their targets completely immune to physical damage, although they can still be targeted by attacks and abilities.

Attack damage
Attack damage is dealt by regular physical attacks. The formula to calculate the exact value is displayed below:

Attack damage types
Physical damage done by attacks is further divided into 4 attack damage types that modify damage based on the target's armor type (from which there also are 4 different types). All physical damage is affected by both armor and armor type. For example, siege creeps do increased damage (150%) against structures, while ranged lane creeps do very little damage to them (35%). This is due to the siege creeps' attack type being "siege" and the ranged creeps' type being "pierce". Siege type is most effective against structure armor type, while pierce damage is the least effective type against it.

Physical damage abilities
Physical damage from abilities is usually unaffected by armor type, as they are not considered to be attacks. There are some exceptions to this. However, if a physical damage ability adds its damage directly to the hero's attack damage, then it is treated like hero attack damage and thus affected by armor types. The hero attack damage type deals 50% to structure armor type (used by all buildings and siege creeps), and 100% to all other types. They are all affected by armor value, but none by evasion and Damage Block (except for and, which are affected by Damage Block).

The following abilities deal physical damage (summoned units, including wards, are not listed):

1 Damage is directly added to the unit's attack damage.

2 Damage from these abilities is affected by armor type as well.

3 Half of damage dealt is physical, the other half magical.

4 Damage is blocked by Damage Block.

Magical
Magical Damage is caused primarily by spells, although not all do magic damage. Magic damage is reduced by magic resistance, and deals higher damage against ethereal units. The majority of abilities in Dota 2 deal magical damage.

All abilities not explicitly listed under another damage type section inflict magical damage.

Pure
Pure Damage is a damage type that is not reduced by magic resistance nor amplified by magical damage amplification like or. It also fully ignores armor and Damage Block. However, it can be reduced or amplified by skills which reduce/amplify every damage type, like or. Pure damage affects spell immune units (since spell immunity does not block damage by itself), but that does not mean that a spell with pure damage can target spell immune units (e.g. deals pure damage, but cannot be cast on spell immune units). It does not affect invulnerable units.

The following abilities deal pure damage:

1 Mist Coil deals pure damage to the caster, but magical damage to the target.

2 Laguna Blade deals pure only when upgraded by, else it deals magical damage.

3 Mystic Snake deals pure damage to units turned into stone by, and magical damage to all others.

4 Whirling Death deals pure damage if it cuts trees within its 300 radius on the same cast, else it deals magical damage.

Spell damage
Spell damage is all damage which is not dealt by physical attacks. This includes all spells which deal magical, physical or pure damage. Even the damage dealt by attack modifiers counts as spell damage, as long as the effect deals its damage in a separate instance from the attack damage.

For heroes, spell damage is amplified based on their intelligence, gaining 1% of amplification per 16 intelligence points (which is 0.0625% per intelligence). Besides intelligence, spells can also be amplified with. The damage amplification sources stack all additively. The amplification does not only affect spell damage dealt against enemies, it also causes damage afflicted to allies or the own unit to get amplified.

Another effect making exclusive use of spell damage is 's Spell Lifesteal.

Flags
Several abilities are flagged certainly, so that they behave differently in certain situations. There are 2 different flags: The HP Removal flag and the No-reflection flag. All spells can be flagged, regardless of what damage type they use.

HP Removal flag
Spells flagged as HP Removal fully ignore any form of damage manipulation (with a few exceptions listed below), means they cannot be amplified, reduced or blocked except by magic resistance in case of magical damage and armor in case of physical damage. They also ignore and do not trigger any on-damage effects, making them unable to cancel consumables for example. Almost every spell flagged as HP Removal deals pure damage. The HP Removal flag also causes damage to ignore invulnerability, however, this is not the always the case.

This flag is usually used on instantly killing effects (this includes expiring summoned as well as with dominated units, and summons dying due to re-summoning), on spells which damage the caster (as health cost) or as a damage delaying effect.

The following abilities instantly kill units (usually by dealing their current or max health as damage). Their damage type is pure, flagged as HP Removal:

1 These spells kill their targets instantly when their health is below the threshold. Although their regular damage type is magical, the killing blow is pure.

2 These spells instantly kill the caster.

3 When all 3 Brewlings die, Brewmaster is instantly killed. Same applies to Phoenix (and the allied hero inside) when the Supernova dies and to the Spirit Bear (without upgrade) when Lone Druid dies.

4 Upon exceeding the max number of allowed units, the oldest persuaded or dominated unit is instantly killed. Dominated units are also instantly killed upon losing the item.

5 These spells instantly kill the target. Sacred Arrow only instantly kills when it is a non-hero, non-ancient creep. Omnislash only instantly kills non-player controlled units, except Roshan.

6 These spells instantly kill targeted illusions.

7 When one Meepo dies, all other Meepos are instantly killed.

The following abilities use HP Removal to create a health cost effect. They are not lethal so units cannot die to them. Their damage type is pure as well, flagged as HP Removal:

1 Units within a radius around Undying (allies and enemies alike) unwillingly pay health for the spell.

The following abilities are flagged as HP Removal for other means, mostly to create a delayed damage effect. Only very few spells which just deal damage are flagged as HP Removal, so they do not cancel consumables. As such, not all of them deal pure damage:

1 These abilities delay damage. The delayed damage is pure and has the HP Removal flag.

2 Heartstopper Aura was supposedly changed to be negative regeneration. However, as evidenced by the game files, its damage type is still pure, flagged as HP Removal.

3 These spells set a unit's health to a certain value. This value can be lower than their current health.

4 These are the only spells which have the HP Removal flagged which deal magical damage. As such, they are still affected by magic resistance and magical damage barriers.

5 Dispersion's damage is based on the received damage type, so it can be physical, magical and pure.

Besides all sources of damage manipulation, the following abilities and items do not react on damage which has the HP Removal flag:

No-reflection flag
The no-reflection flag causes every spell which has the flag to not interact with the damage of spells which also have the flag. This is to prevent infinite damage loops (for example 2 opposing heroes with ).

Ultimately, the below listed spells can never proc each other due to the flag. Besides these, also does not amplify outgoing damage which has the no-reflection flag and  does not proc on flagged damage.

The following sources of damage are flagged:

Removed damage types
The following damage types were removed in patch 6.82 in order to simplify the game mechanics.

Composite
Composite damage (also known as mixed damage) was a damage type that was reduced by both armor and magic resistance. It pierced spell immunity and did not affect ethereal units. This damage type was used by, , , 's backlash damage, and. All of them were changed to physical damage, except for the backlash damage from the Spirit Bear, which was changed to pure damage.

Universal
Universal damage was a damage type that pierced spell immunity and was affected by magic resistance. This damage type was previously used by, , 's initial damage, , upgraded , , and. Doom, Midnight Pulse, Flaming Fists and Aghanim's Scepter upgraded Laguna Blade were changed to deal pure damage, allowing them to still pierce spell immunity, while Pulverize, Echo Slam's initial damage and March of the Machines were changed to deal magical damage, and thus no longer pierce spell immunity.