Fearful Aura is an Exotic Powercard in Bloons Card Storm, introduced in version 4.0. It reduces the ATK of all enemy Monkeys by 20 (to a minimum of 0), including any Monkeys placed after its activation, until the end of the opponent's next turn. This card is exclusive to Dreadbloon and is not found in the Collection.
Prepare some board clear cards in case Dreadbloon uses Fearful Aura to discourage you from using Monkeys to defend against its rushes.
When it comes to Dreadbloon itself, Fearful Aura can limit the capability to create big bursts of damage to Dreadbloon, but since it lasts only one round it's not usually a problem to just resume attacking with your current Monkeys. Wait till Fearful Aura ends before doing large damage bursts such as Missile Launcher + Berserker Brew.
Avoid low ATK Monkeys. Notably, 20 lost ATK is enough to neutralise Barrel of Monkeys without a buff such as Gwendolin's Heat It Up.
Dreadbloon has Bed Time on stages 1 and 3, which it can use on Monkeys with 50 or less ATK after using this card, such as Mine Supervisor (40).
All stages of Dreadbloon have 3 Fearful Auras in their decks.
Sometimes, Dreadbloon may use this card more than once in a single turn.