Looking back, we will find the whole literature using it as a concept to create poems and stories.

A doppelganger in German folklore was considered a wraith or apparition of a person alive.

In ancient times it was believed that there was an invisible replica of every man, bird or even beast and meeting them was a sign insinuating one's death would be coming soon.

There was a cornucopia of myths, some suggesting gothic features while others just made normal stories.

Besides, most of the mythology named it a harbinger of death. So if you find your lookalike, you will be reaching the end.

The doppelganger became the symbol of horror literature, portraying your lookalike as exactly your apparition. "In The Double (1846), by Fyodor Dostoyevsky, for example, a poor clerk, Golyadkin, driven to madness by poverty and unrequited love, beholds his own wraith, who succeeds in everything at which Golyadkin has failed. Finally, the wraith succeeds in disposing of his original."