Doppleganger, Dark side or What ?

"A person who seems to be an exact copy of yourself. Doppelgangers usually cause trouble by acting as yourself and interacting with other people. " 

In fiction and folklore, a doppelganger is a paranormal double of a living person . Doppelgangers often are perceived as a sinister form of bilocation and are regarded by some to be harbingers of bad luck. In some traditions, a doppelganger seen by a person's friends or relatives portends illness or danger, while seeing one's own doppelganger is said to be an omen of death.

This phenomenon different type than seeing a ghost . If you see a ghost ,you'll see unknown dead person but doppleganger is a shadow of the living person and maybe it's you or your friends .

Abraham Lincoln's Case

 A dream or illusion had haunted Lincoln at times through the winter. On the evening of his election he had thrown himself on one of the haircloth sofas at home, just after the first telegrams of November 7 had told him he was elected president, and looking into a bureau mirror across the room he saw himself full length, but with two faces. It bothered him; he got up; the illusion vanished; but when he lay down again there in the glass again were two faces, one paler than the other.

He got up again, mixed in the election excitement, forgot about it; but it came back, and haunted him. He told his wife about it; she worried too. A few days later he tried it once more and the illusion of the two faces again registered to his eyes. But that was the last; the ghost since then wouldn't come back, he told his wife, who said it was a sign he would be elected to a second term, and the death pallor of one face meant he wouldn't live through his second term.

Emilie Sagee's Case

One of the most fascinating reports of a doppelganger comes from American writer Robert Dale Owen who was told the story by Julie von Güldenstubbe. In 1845, when Julie was 13, she attended Pensionat von Neuwelcke, an exclusive girl's school near Wolmar in what is now Latvia. One of her teachers was a 32-year-old French woman named Emilie Sagée. And although the school's administration was quite pleased with Sagee's performance, she soon became the object of rumor and odd speculation. Sagee, it seemed, had a double that would appear and disappear in full view of the students.

In the middle of class one day, while Sagee was writing on the blackboard, her exact double appeared beside her. The doppelganger precisely copied the teacher's every move as she wrote, except that it did not hold any chalk. The event was witnessed by 13 students in the classroom. A similar incident was reported at dinner one evening when Sagee's doppelganger was seen standing behind her, mimicking the movements of her eating, although it held no utensils.

The doppelganger did not always echo her movements, however. On several occasions, Sagée would be seen in one part of the school when it was known that she was in another at that time. the students could clearly see Sagee in the school's garden gathering flowers. Suddenly,Sagee's doppelganger appeared in her chair - while the real Sagee could still be seen in the garden. The students noted that Sagee's movements in the garden looked tired while the doppelganger sat motionless. Two brave girls approached the phantom and tried to touch it, but felt an odd resistance in the air surrounding it. One girl actually stepped between the teacher's chair and the table, passing right through the apparition, which remained motionless. It then slowly vanished !!

Sagee claimed never to have seen the doppelganger herself, but said that whenever it was said to appear, she felt drained and fatigued. Her physical color even seemed to pale at those times.

( Enigma , Myst Blog)