Unique Attack Modifier

Unique Attack Modifiers (formerly known as Orb Effects) are special attack 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. Not all attack modifiers count as Unique Attack Modifiers, such as Huskar's Burning Spear or the purchasable Diffusal Blade. This means that Heroes can combine a unique attack modifier with other non-unique attack modifiers like Burning Spear or Searing Arrows, making use of both at the same time

Priority
Multiple unique attack 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) and Mjollnir (chance-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* (in Ability Draft the first UAM ability obtained will override later ones)
 * 3) Standard Modifiers - Modifiers granted by items (an item will take priority depending on which is the oldest in your inventory, or in the case of illusions the first slot in reading order)

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

When attacking units (such as Spell Immune heroes or buildings) that are immune to certain Unique Attack Modifiers, other UAMs that can proc will be used, even if they are not prioritized. An example of this is having an Eye of Skadi and a Desolator, if the Skadi has higher priority. Because buildings are not affected by the Skadi, the Desolator's effects will be used instead.

There is one exception: Eye of Skadi and Lifesteal can be active at the same time. (Lifesteal is granted by Morbid Mask, Helm of the Dominator, Mask of Madness, or Satanic.)