Unique Attack Modifier

Unique Attack Modifiers (abbreviated UAM; formerly known as Orb Effects) are special attack modifiers that cannot be used simultaneously with each other—one always takes priority. They may be provided by abilities (e.g. Anti-Mage's ), or items (e.g. ).

Unique attack modifiers do work simultaneously with non-unique attack modifiers. For example, Huskar carrying a Desolator and using Burning Spear will proc both modifiers on every attack.

Priority
Multiple unique attack modifiers do not stack. One always takes priority, as follows:

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

When attacking units that are immune to certain Unique Attack Modifiers (such as Spell Immune heroes or buildings) with an autocast modifier, other UAMs that it is vulnerable to will be used, even if they lower in priority. For example, buildings are immune to and, but if the hero is carrying a , it will proc instead. This does not apply to non-autocastable UAMs like —they still follow the above priority order regardless of a target's spell immunity.