NOTE: This is about the number of rounds the creature effected by the Fear effect, not about the duration of the Fear Cone itself.
These read as:
Fear (Su or Sp) Fear attacks can have various effects.
Fear Aura (Su) The use of this ability is a free action. The aura can freeze an opponent (as in the case of a mummy's despair) or function like the fear spell. Other effects are possible. A fear aura is an area effect. The descriptive text gives the size and kind of the area.
Fear Cone (Sp) and Ray (Su) These effects usually work like the fear spell.
The Mummy's Despair reads as follows:
All creatures within a 30-foot radius that see a mummy must make a DC 16 Will save or be paralyzed by fear for 1d4 rounds. Whether or not the save is successful, that creature cannot be affected again by the same mummy’s despair ability for 24 hours. This is a paralysis and a mind-affecting fear affect. The save DC is Charisma-based.
Table: Potions gives sample prices for potions created at the lowest possible caster level for each spellcasting class. Note that some spells appear at different levels for different casters. The level of such spells depends on the caster brewing the potion.
Table: Scrolls gives sample prices for scrolls created at the lowest possible caster level for each spellcasting class. Note that some spells appear at different levels for different casters. The level of such spells depends on the caster scribing the scroll.
And finally, the referenced fear spell:
Range 30 ft. Area cone-shaped burst Duration 1 round/level or 1 round; see text Saving Throw Will partial; Spell Resistance yes
An invisible cone of terror causes each living creature in the area to become panicked unless it succeeds on a Will save. If cornered, a panicked creature begins cowering. If the Will save succeeds, the creature is shaken for 1 round.
So putting everything in a concise manner:
Potions and Scrolls tend to be the minimum caster level required to cast the spell; but don't have to be
Fear Aura (Despair) spells out how long someone should be susceptible to fear for
Fear Cones (at least this one) doesn't spell out how long it is supposed to last; which is strange. The rules say it's similar to the Fear spell, but has no caster level associated with it in the Gaki's case and doesn't have one in the example case (where Fear Cone is defined)
The fear spell says it lasts for 1 round per caster level (upon failure)
Here are the options I can see:
A. The Panicked effect from the Fear Cone lasts 1 round because it is undefined
B. The Panicked effect from the Fear Cone lasts 1 round because it is undefined, and causes shaken if they pass their Will save (as per the spell)
C. The Panicked effect from the Fear Cone lasts 7 rounds*, because that is the minimum caster level of the spell, and causes shaken for 1 round on a passed will save
- The bard gets it as a 3rd level spell but is caster level 7 when he casts it; thus the minimum is 7.
I am open to other interpretations, and I am assuming that version B is correct, as running for 7 rounds effectively removes someone from the encounter (especially as they will be several hundred feet away after that.) I'm mostly looking for a RAW answer and will worry about balancing the encounter after I know how it's supposed to work.