Abduction...

After heaven had been moved away from earth,

After earth had been separated from heaven,

After the name of man had been fixed;

After An had carried off heaven,

After Enlil had carried off earth,

After Ereshkigal had been carried off into Kur as its prize...
Link.

There are two main references in Mesopotamian (Sumerian /Akkadian) stories that correspond to the modern concept of a Close Encounter.

The first has been quoted above, from 'The Sumerians: Their History, Culture, and Character'
 By Samuel Noah Kramer.

The second also comes from the epic of Gilgamesh...The ominous dreams Enkidu suffers as he and Gilgamesh journey deep into the ceder forest to kill the protector of the trees, the monster Humbaba..

Here is Enkidu's third, and final dream:

Then, at midnight, sleep left him; he got up and said to his friend, 'Did you call me, or why did I wake? Did you touch me, or why am I terrified? Did not some god pass by, for my limbs are numb with fear? My friend, I saw a third dream and this dream was altogether frightful. The heavens roared and the earth roared again, daylight failed and darkness fell, lightnings flashed, fire blazed out, the clouds lowered, they rained down death. Then the brightness departed, the fire went out, and all was turned to ashes fallen about us.

The phenomenon described in modern times as the experience of Satanic abuse, and of alien abduction, including the description Livy gives of the cult of Dionysos brought into Roman society by Paculla Annia...are powerful, traumatic, and will be trans-formative...anyone undergoing abduction will be changed forever...

Livy:

Men were fastened to a machine and hurried off to hidden caves, and they were said to have been rapt away by the gods; these were the men who refused to join their conspiracy or take a part in their crimes or submit to pollution. They formed an immense multitude, almost equal to the population of Rome; amongst them were members of noble families both men and women. It had been made a rule for the last two years that no one more than twenty years old should be initiated; they captured those to be deceived and polluted.

Unfortunately, for those who wish to control it, the location of this experience is impossible to fix in time or space.

• When it is believed that the origin of abduction is extra or ultra-terrestrial, the entities responsible are beyond the stars, and beyond our phase of the multiverse.
• When the entities are supposed to be daemonic or angelic, there is no book that provides a sure way to contact them.
• When the agent is terrestrial, and human, 'they' are people with wealth and power, who prey like vampires upon the young and innocent...and are protected by the laws of the state.

An attempt to locate the true origin of the abduction as entirely within the human mind appears simpler.

Though Homer muddies the water somewhat, by saying as I would say:

For two are the gates of shadowy dreams, and one is fashioned of horn and one of ivory. Those dreams that pass through the gate of sawn ivory deceive men, bringing words that find no fulfillment. But those that come forth through the gate of polished horn bring true issues to pass, when any mortal sees them. But in my case it was not from thence, methinks, that my strange dream came...

Whitley Strieber (whose diary you can read here )  sounds something like Enkidu in: "Summer of Promise, Summer of Danger," July 12th, 2003  if you replace his word visitors with Gods:

"Remember this: earth has given birth to something we call the human mind. But the visitors view it as a precious resource of innovation and, ultimately, of ecstasy. They are indifferent to power, but willing to use dark appearances to give lessons."

Terence McKenna made a similar point when he wrote:

 "We are part of a symbiotic relationship with something which disguises itself as an extra-terrestrial invasion so as not to alarm us."

Alternatively, Stanislav Grof describes a firing of neurons located within synaptic networks deep inside the oldest structures of the brain...Birth memories create the basic perinatal matrix, and  'Systems of Condensed Experience' are tagged together by memories forged during moments of extreme emotional charge...the emotional tone defines each system....an intrusive replay of the birthing experience corresponds in so many ways to abduction.

Nevertheless...
No matter how often we read of the negative aspects of the abduction experience, there is more to it than pathology.

It is after all, the experience of initiation.

Last word goes to Publius Aelius Aristides Theodorus (Greek: Αἴλιος Ἀριστείδης; 117–181 CE) Oration 48.32 :

For there was a feeling as if taking hold of the god and of clearly perceiving that he himself had come, of being midway between sleeping and waking, of wanting to look, of struggling against his departure too soon; of having applied one’s ears and hearing some things as in a dream, some waking; hair stood straight, tears flowed in joy; the burden of understanding seemed light. What man is able to put these things into words? Yet if he is one of those who have undergone initiation, he knows and is familiar with them.