The Deep
A phobia is defined as an excessive and irrational fear reaction.
Those ailing from it experience a deep sense of dread, anxiety, and sometimes panic, or that's what the modern human psychologists that didn't know any better thought.
"Irrational," they say.
Maybe that was the truth.
Maybe it seemed groundless and absurd to some, but to those more informed, it wasn't always all that unreasonable.
Back when humans had not reached the stars, when they thought the earth was the center of the universe, old shamans and village elders had a different explanation for such behavior.
They thought that some individuals that were more in tune with the unknown, with the 'unseen' ones, and those that could peek through the curtain of reality without realizing it were able to know things that normal individuals could not.
Most of the time they could not understand what they were seeing.
At times it would come to them as nightmares, horrid images of things that should not be.