Rules: Frightful Presence

A dragon’s frightful presence is an extraordinary ability. It works even in antimagic areas.
Frightful presence is a mind-affecting fear ability that takes effect whenever a dragon attacks, charges, or merely flies overhead. A dragon can inspire fear by flying overhead at an altitude low enough to place foes with the radius of the effect, which is 30 feet × the dragon’s age category (usually at least 150 feet, since most dragons gain this ability at the young adult stage). A dragon’s frightful presence also takes effect whenever the dragon charges or attacks in any way (with natural weapons, spells, or a breath weapon).
Using frightful presence is part of whatever action triggers it. A dragon does not have to take a separate action to use the power; however, a dragon can suppress its frightful presence ability as a free action.
A creature must be able to see the dragon for its frightful presence ability to take effect. If the dragon is invisible or has total concealment, the ability does not work. Once the ability takes effect, however, the consequences persist for the full duration, even if the dragon later passes from sight. Creatures within the ability’s radius are not affected if they have more Hit Dice than the dragon, or if they are dragons themselves.
A potentially affected creature that succeeds on a Will save (DC 10 + 1/2 dragon’s HD + dragon’s Cha modifier) remains immune to that dragon’s frightful presence for 24 hours. (This temporary immunity occurs only on a successful save. If a creature doesn’t have to make a save because it cannot see the dragon, it is not immune and must make a save when it does see the dragon.) On a failure, creatures with 4 or fewer HD become panicked for 4d6 rounds, and those with 5 or more HD become shaken for 4d6 rounds.
As an extraordinary ability, frightful presence remains effective even when the dragon assumes a different form. Bronze, gold, and silver dragons, which have the ability to assume an alternate form, usually suppress their frightful presence ability when using assumed forms, to avoid compromising their disguises. If they wish to avoid fighting, however, they can use their frightful presence ability if they are challenged when in their assumed forms.