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An aura is a type of area of effect (AoE) spell.

Definition

Auras have four basic characteristics:

• They are AoE spells, based on the position of the caster, otherwise known as point blank area of effect (PBAoE) spells.
• They are instant cast, and have no cooldown.
• They have an infinite duration, as long as the affected target is within range of the caster, and the caster is alive.
• They are not dispellable.

Player Auras

Each of these auras are party only.

Draenei auras:

• Heroic Presence - Hit increase (Hunters, Paladins and Warriors)
• Inspiring Presence - Spell Hit increase (Priests, Mages and Shaman)

Druid auras:

• Leader of the Pack - Crit increase (effect of Feral forms)
• Moonkin Aura - Spell Crit increase (effect of Moonkin Form)
• Tree of Life Aura - Healing Received increased by a % of the Druid's spirit (effect of Tree of Life Form)

Hunter auras:

• Aspect of the Pack - Run Speed increase, become dazed when hit
• Aspect of the Wild - Nature Resistance increase
• Trueshot Aura - Attack Power increase

Paladin auras:

• Devotion Aura - Armor increase
• Concentration Aura - Prevents spell pushback
• Crusader Aura - Mounted Speed increase
• Fire Resistance Aura - Fire Resistance increase
• Frost Resistance Aura - Frost Resistance increase
• Retribution Aura - Deals Holy damage when hit
• Sanctity Aura - Holy damage increase
• Shadow Resistance Aura - Shadow Resistance increase

Some classes also have pets or totems with auras:

Shaman auras: (used by stationary totems with varying lifespans)

• Disease Cleansing Totem - Disease removal
• Earthbind Totem - Snare
• Fire Resistance Totem - Fire Resistance increase
• Flametongue Totem - grants a weak Flametongue Weapon
• Frost Resistance Totem - Frost Resistance increase
• Grace of Air Totem - Agility increase
• Grounding Totem - absorbs a spell
• Healing Stream Totem - Heal
• Magma Totem - Fire damage
• Mana Spring Totem - Mana regeneration
• Mana Tide Totem - powerful Mana regeneration
• Nature Resistance Totem - Nature Resistance increase
• Poison Cleansing Totem - Poison removal
• Stoneclaw Totem - Taunt
• Stoneskin Totem - Reduces melee damage taken
• Strength of Earth Totem - Strength increase
• Totem of Wrath - Spell Hit and Spell Crit increase
• Tranquil Air Totem - Reduces Threat
• Tremor Totem - Fear, Charm and Sleep removal
• Windfury Totem - grants a weak Windfury Weapon
• Windwall Totem - Reduces ranged damage taken
• Wrath of Air Totem - Spell Damage increase

Warlock auras:

• Blood Pact - Stamina increase (used by Imp)
• Paranoia - Stealth Detection increase (used by Felhunter)

Creatures who have auras

Creature auras effect players.

Baron Rivendare of Stratholme has "Unholy Aura", which does periodic shadow damage.

Lord Alexei Barov of Scholomance also has "Unholy Aura".

As does Atiesh, Hand of Sargeras