FASA Games, Inc.

what kind of being can be affected by fear effects?

-horrors (i doubt, but perhaps a gnasher?)
-horror constructs (does a cadaver man fear anything?)
-spirits
-tasked spirits
-illusions (like astral horror)
-dragons

?

Horrors and Horror constructs are not affected by fear effects.
Illusions having no emotions or mind, cannot be affected by fear effects.
Dragons and Spirits can be affected by fear effects.
Tasked Spirits are Game Master Discretion. In general if the tasked spirit summoned is a creature, it can be affected by fear such as astral mount or blood servitor. If it is undead, such as animate skeleton or bone walker, they are unaffected by fear as they are undead constructs. I'd rule astral maw cannot be affected by fear, as it is Horror-like for example.

A Game Master might also rule that a Dragon that has the Fear power is either immune to fear or effects that use fear require a greater Result Level at their discretion as well.