Aura

Auras are passive abilities that grant a buff or debuff to units in an area of effect around the holder, or in some cases, over a short period at a targeted point or unit. By default, the buffs and debuffs linger on the affected units for 0.5 seconds after not being affected by the source any more, however, some auras have a different value. Generally, aura buffs and debuffs are not dispellable and multiple auras of the same kind (like Ring of Aquila and Vladmir's Offering) as well as identical auras do not stack, but there are various exceptions.

Most auras cannot be controlled. They always affect units around the holder. Some auras can be toggled on or off. A few auras also have an extra active component, which ranges from temporarily boosting the aura to deciding whether it should affect surrounding heroes only or not. The active components or the toggle ability are treated like a regular spell, meaning they cannot be used or toggled while silenced or disabled. Beside these, there also are temporary auras, which are provided for a certain time period by casting a spell.

There is no set rule for which units are generally affected by auras and which are not. It depends on the aura which units it affects and which it does not. If a unit does not meet the requirements for the aura, it is not affected. There are auras which affect only ranged units, or melee units, only heroes, or only non-heroes. As a rule of thumb, positive auras usually affect allied units (including the holder of the aura), while negative auras affect enemy units. There are a few exceptions.

Auras usually also affect invisible units, and units in the Fog of War and are bestowed by them (which often allows to detect if an invisible enemy is nearby). However, almost all auras do not affect invulnerable or hidden units.

Illusions can bestow most passive auras, but they usually do not benefit from them.