Attack Modifier

Attack modifiers are modifiers which apply an effect to a unit's basic attacks. These effects can widely vary, from healing, to damaging or even disabling effects. Most of these modifiers have their own rules. For example, some modifiers may not stack with others, some may fully stack, some may be for melee units only and others for ranged or both. Attack modifiers can be active, in which case they require to be used manually, though most have an autocast option, but they also can be passive, proccing, or having a chance to proc on each attack.

Stacking
There is no set rule of how attack modifiers stack. In most cases, attack modifiers stack with each other.

Common attack modifiers
Common attack modifiers are attack modifiers which are not unique abilities, but are seen commonly on many heroes and items. The only differences between them are their values and how they are activated or acquired, some being applied on each attack, others being chance based.

Abilities which simply grant or reduce attack speed (e.g. or ) or attack damage (e.g.  or ) are not attack modifiers in that sense, as they directly enhance the attack, instead of granting a modification.

Critical strike
Critical strike causes the attacks to deal multiplied damage. Most critical strikes are chance-based, but not all. Critical Strikes fully stack with other attack modifiers. However, they do not fully stack with themselves. Multiple sources of critical strike have all their own proc chance. But if multiple of them proc on the same attack, only the one with the highest damage multiplier is applied. If they have the same multiplier, only one of them is applied still.
 * Examples of critical strike are and

Cleave and splash
Cleave causes the unit's attack to deal damage in a trapezoid area in front of the attacking unit. The damage is based on the unit's attack damage values. Cleave can only be used by melee units, ranged units cannot cleave. Cleaves fully stack with other attack modifiers. Multiple sources of cleave on the same unit work fully independently of each other. Each source applies its full damage within its area, without interacting with the other cleave sources.
 * Examples of cleave are, and.

Splash causes the unit's attack to deal damage in a circular area around the attacked unit. Splash can only be used by ranged units, melee units cannot splash. Splash fully stacks with other attack modifiers. Multiple sources of splash on the same unit work fully independently of each other. Each source applies its full damage within its area, without interacting with other splash sources.
 * Examples of splash are and.

Bash
Bash causes the unit's attack to stun the target and in some cases to also deal additional damage. Most bash abilities are chance-based. Bash fully stacks with other attack modifiers, except with other bashes. Multiple sources of bashes do not stack at all. The later acquired bash has absolutely no effect, only the first acquired bash works.
 * Examples of bash are, and.

Lifesteal
Lifesteal causes the unit's attack to heal the attacking unit based on the damage dealt to the attack target. Lifesteal fully stacks with other attack modifiers. Multiple sources of lifesteal stack additively with each other. Each source of lifesteal heals the attacking unit by its given value, and does not interfere with other lifesteal sources.
 * Examples of lifesteal are, , and.

Mana break
Mana break causes the unit's attack to burn a portion of the target's mana and deal damage based on the amount of mana burned. Mana Break fully stacks with other attack modifiers. Multiple sources of mana break stack additively with each other, with the only exception being 's Mana Break, which does not stack with that from. In this case, the later acquired one works.
 * Examples of mana break are, and.

On-hit effects and attack modifiers
Besides the common modifiers, many heroes, units and items have attack modifiers which are unique to them, meaning they can be only found on those units or items. To correctly understand and predict interactions between these various mechanics, on-hit effects must be distinguished from attack modifiers. In general,


 * an attack modifier is applied to an attack at its inception. In some cases this is visually apparent on the attack projectile for ranged heroes (e.g. red projectile for ), but not all attack modifiers have visual effects. As these modifications are calculated at the start of the attack, changes during the flight time of an attack projectile (like picking up an item) will generally not affect these attacks that were launched earlier.
 * an on-hit effect is only applied at the time the attack arrives at its target. (Whether it hits or misses is not relevant yet at that point.) By definition, any ability or item that produces an on-hit effect cannot have a visual effect. This is because at the time the projectile is in flight, the decision to apply the on-hit effect has not yet been made. Conversely, changes during the flight time of a projectile can influence on-hit effects—in fact, the on-hit effect is not even tied to any particular attack, rather it is tied to an ability or item.

Note that the above descriptions are only a general outline and the game can always add specific additional rules or exceptions in its code. However, some consequences can be logically derived from these descriptions:
 * attack modifiers are mostly nullified if the target successfully evades an attack and causes a miss. Because the attack modifier is carried on the attack, and the attack fails, the modifier fails too.
 * on-hit effects have an opportunity to perform actions before evasion, but may still be coded to take evasion into account. For example, disables evasion as an on-hit effect, while 's Overload explicitly does nothing when the attack is evaded.
 * multi-attack abilities that apply modifiers (i.e. on and ) will generally apply all attack modifiers, but generally not on-hit effects.  This is because most on-hit effects are specified to happen only on a "first" or "next" attack, and only one of the attacks of the multi-attack ability will meet this condition.  The other attacks will also check for on-hit effects, but as separate instances.

Active attack modifiers
Active attack modifiers are modifiers which must be actively used on each attack to apply its effects. They also can be set to autocast, causing each attack to apply the effect if the hero can support their costs.

When set to autocast, they still count as a regular attack. When used manually, they partly count as a spell cast. This means, unlike regular attacks, they do not cause any aggro from lane creeps. However, they do not count as spells in any other scenario, meaning they cannot be used when attacking is restricted and do not proc anything which triggers on spell cast.

Orb walking
Issuing an attack command on an enemy hero causes all nearby enemy creeps and towers to switch their aggro to the attacking unit. This is not the case for casting spells on enemy heroes. Orb-walking is the act of manually casting active attack modifiers like other active abilities, instead of using autocast and right-click or auto-attacks. When used manually, the attack is partially treated as a spell cast. This causes the hero to not draw aggro from nearby enemy creeps, making it possible to harass an enemy in the lane without the creeps and even towers refocusing their attacks on the harassing hero as they normally would when using regular attacks or autocast. However, the effect still counts as an attack and not a spell cast in regards of on-cast effects. It still uses the hero's attack speed and animations and still puts the attack on cooldown normally.

Origin of the term "orb"
In Warcraft 3, unique attack modifiers are called "orb effects". This is due to the items which grant the attack modifiers commonly being orbs (for example, Orb of Venom, Orb of Darkness, Orb of Lightning, Orb of Corruption, etc). A characteristic of these orb effects is that they do not stack with each other. The items being portrayed as orbs serves as a metaphor, as stacking real sphere-shaped objects is very difficult to do. Since DotA is a custom map on Warcraft 3, it made use of the abilities of these orb items, and the term "orb" was used to describe that attack modifiers based on those items do not stack. Therefore, unique attack modifiers are referred to as "orb effects" in DotA, just like how they are in Warcraft 3. The term was changed to "Unique Attack Modifier" in Dota 2, while "orb effect" was dropped, however, many players which came from DotA still refer to these modifiers as orb effects. The term "orb walking" originates therefore from Warcraft 3, describing the same technique as described earlier.

Later usage of the term
A later usage of the term "orb walking" refers to using attacks or active attack modifiers to achieve stutter stepping. "Stutter stepping" is the act of cancelling the backswing animation of an attack, allowing the unit to move between attacks, following the target, instead of standing and waiting for the backswing to finish. This old technique, which originated from Starcraft and carried over to Warcraft and therefore also to DotA, was commonly used together with the orb-walking technique. This is because of how manually casting active attack modifiers behaves, as compared to regular attacks. During the cast time of a manually cast active attack modifier, the player can spam the move command, which does not cancel the ongoing cast, but the first move command after the cast point is reached cancels the backswing, so the hero moves almost immediately after the attack launched. However, doing that during a regular attack does cancel the regular attack, causing the unit to move immediately, so the player must time the move command after the attack launched. This means stutter stepping was much easier to do with casting active attack modifiers, as timing for the move command was not required, allowing for much more effective stutter stepping. Due to this, orb walking and stutter stepping were very commonly used together, so commonly that players started to call the move just orb walking, even though it was orb walking and stutter stepping together. This resulted in the community to commonly refer to stutter stepping as orb walking, even though stutter stepping can be done with regular attacks as well. The term stutter stepping became less known as a result. However, outside of Dota, the technique is still called stutter stepping, which may cause some confusion when mentioning the technique in other communities (like Starcraft, League of Legends, Command and Conquer and other RTS and Dota-like games), as they most probably only know it as stutter stepping.

Unique attack modifiers
Unique Attack Modifiers (abbreviated UAM; formerly known as Orb Effects) were attack modifiers that could not be used simultaneously with each other—one always took priority.

Unique attack modifiers did work simultaneously with non-unique attack modifiers.

Stacking priority
Multiple unique attack modifiers did not stack. One always took priority, as follows:
 * 1) Unique active attack modifiers that were cast manually.
 * 2) Unique active attack modifiers set to auto-cast.
 * 3) Unique attack modifiers granted by items.

In Ability Draft, the first obtained UAM ability always overrid later ones. Items held by a hero prioritised by age. Items held by illusions prioritised by inventory slot in reading order.

When attacking units that were invalid targets for certain Unique Attack Modifiers (such as spell immune heroes or buildings) with an auto-cast modifier, other UAMs that it was vulnerable to would be used, even if they were lower in priority. For example, spell immune heroes are immune to, but if the hero was carrying a , it would proc instead. This did not apply to non-autocastable UAMs like —they still followed the above priority order regardless of a target's spell immunity.

Version history
Modificador de ataque Модификаторы атаки 攻击特效