A dragon attacks, which activates its frightful presence. Everyone in the party has at least 5 HD, but fewer HD than the dragon. At least one party member is affected, and they are shaken.
The following round, the dragon breathes fire and activates their frightful presence a second time. What happens?
This special quality makes a creature’s very presence unsettling to foes. Activating this ability is a free action that is usually part of an attack or charge. Opponents within range who witness the action may become frightened or shaken. The range is usually 30 feet, and the duration is usually 5d6 rounds. This ability affects only opponents with fewer Hit Dice than the creature has. An opponent can resist the effects with a successful Will save (DC 10 + 1/2 the frightful creature’s racial HD + the frightful creature’s Cha modifier; the exact DC is given in the creature’s descriptive text). An opponent that succeeds on the saving throw is immune to that same creature’s frightful presence for 24 hours. On a failed save, the opponent is shaken, or panicked if it has 4 Hit Dice or fewer. Frightful presence is a mind-affecting fear effect.
Format: frightful presence (60 ft., DC 21); Location: Aura.
Possibly Relevant Rules
Becoming Even More Fearful: Fear effects are cumulative. A shaken character who is made shaken again becomes frightened, and a shaken character who is made frightened becomes panicked instead. A frightened character who is made shaken or frightened becomes panicked instead.
Frightful Presence is Extraordinary while Fear is Supernatural or Spell-like. Does this mean that Frightful Presence produces a supernatural fear effect? Or is the fear generated by Frightful Presence unrelated to the supernatural or spell-like Fear effect?
There is a rule for magic effects that in general, effects with the same name tend to only affect duration rather that change the actual effect. So, could the fear generated from Frightful Presence stack with itself (the cumulative effect mentioned in the possibly relevant rule above) to take a character from Shaken to Frightened? Or would that run afoul of the rules about stacking effects?
That rule, however, is listed under the more general heading of Combining Magic Effects, and it specifically mentions spells, so it is unclear if it is at all relevant since Frightful Presence is Extraordinary:
Possibly Irrelevant Rules
The same spell can sometimes produce varying effects if applied to the same recipient more than once. Usually the last spell in the series trumps the others. None of the previous spells are actually removed or dispelled, but their effects become irrelevant while the final spell in the series lasts.