Unique Attack Modifier

Unique Attack Modifiers (formerly known as Orb Effects) are special modifiers that alter a Hero's basic attack to provide an additional effect. An example of this is Morbid Mask, which grants the lifesteal effect. Certain Hero abilities are Unique Attack Modifiers, such as Anti Mage's Mana Break, Broodmother's Incapacitating Bite. All Items that grant Unique Attack Modifiers are purchased from the Artifacts shop, or the Secret Shop. Not all attack modifiers count as Unique Attack Modifiers.

Priority

Multiple modifiers do not stack; for each attack one modifier always takes priority. The order of priority is as follows:

1. Conditional Modifiers - Modifiers that only occur on some attacks and are not controlled by the player, such as Maelstrom (chance-based), Mjollnir (chance-based), and Geminate Attack (cooldown-based). If a Conditional Modifier fails to proc then a Standard or Ability Modifier will be present on the attack (if applicable)
2. Ability Modifiers - Modifiers granted by Hero abilities*
3. Standard Modifiers - Modifiers granted by items, with the oldest one in a Hero's inventory taking priority (priority can be shifted by dropping an item and picking it up again)

* UAMs from hero abilities, such as Viper's Poison Attack, will only be overridden by conditional modifiers if they are set to Autocast. If they are Manually cast, they cannot be overridden.

There are two known exceptions: Eye of Skadi and Lifesteal can both be active at the same time. (Lifesteal is granted by Morbid Mask, Helm of the Dominator, Mask of Madness, or Satanic.) Eye of Skadi will also stack with Clinkz Searing Arrows.

List of Unique Attack Modifiers

Items that Grant Unique Attack Modifiers

Morbid Mask Grants 15% Lifesteal	Helm of the Dominator Grants 15% Lifesteal
Mask of Madness Grants 17% Lifesteal	Satanic Grants 25% Lifesteal
Diffusal Blade Burns 20 (36) Mana per attack	Desolator Attacks reduce target Armor by 6
Maelstrom Grants a 25% chance to release Chain Lightning on attacks Only counts as a modifier when it procs	Mjollnir Grants a 25% chance to release Chain Lightning on attacks Only counts as a modifier when it procs
Orb of Venom Attacks deal 3 Damage per second and Slow enemy movement (by 4% if holder is ranged and 12% if melee) for 4 seconds	Eye of Skadi Attacks Slow enemy movement by 30% and attack speed by 20%

Hero Abilities that Grant Unique Attack Modifiers

Mana Break (Anti-Mage Ability) Burns 28/40/52/64 Mana per attack	Frost Arrows (Drow Ranger Ability) * Slows enemy movement by 11%/24%/37%/50% for 1.5 seconds
Caustic Finale (Sand King Ability) Causes units to explode if killed under its effects	Impetus (Enchantress Ability) * Deals 15%/20%/25% of the distance traveled as pure damage
Incapacitating Bite (Broodmother Ability) Slows target by 10%/20%/30%/40% and causes them to miss 10%/15%/20%/25% of the time	Poison Attack (Viper Ability) * Slows target movement and attack speed by 10%/20%/30%/40% and deals 10/16/22/28 damage per second
Geminate Attack (Weaver Ability) Adds an extra swarm to each attack	Burning Spear (Huskar Ability) * Deals 4/8/12/16 damage per second. Stacks with itself
Fury Swipes (Ursa Ability) Causes consecutive attacks to deal 15/20/25/30 extra damage	Searing Arrows (Clinkz Ability) * Deals 20/30/40/50 extra damage
Melting Strike (Invoker's Forged Spirit Ability) Reduces the target's armor by 1 every attack	Glaives of Wisdom (Silencer Ability) * Deals 30%/45%/60%/75% of Silencer's Intelligence as extra damage
Arcane Orb (Outworld Destroyer Ability)* Deals 6%/7%/8%/9% of remaining Mana as pure damage

* This modifier can be cast manually or placed on autocast. Using this modifier effect requires mana or health. If it is cast manually, it can be used to orb walk.

Orb walk

Typically when you right-click on an enemy hero, the nearby creeps will agro you, and attack you. When you cast spells on enemy heroes this is not the case.

Orb-Walking involves using abilities that have Unique Attack Modifiers. Select the ability once and click on an enemy hero, this is now considered casting an ability so nearby enemy creeps will not attack you. You can repeat this as many times as necessary.

On the contrary, however, if you enable auto-cast for the Unique Attack Modifier and right-click on a hero creeps will attack you.