Doppelgängers, also known as Shadow-Selves or Mortal Shadow Selves, are a supernatural occurrence that were created by Nature as a result of Silas and Amara becoming true immortals after consuming Qetsiyah's immortality elixir. The purpose of this supernatural species is to maintain the natural balance by dying in place of their immortal progenitors. For this reason, doppelgängers have existed for at least 1,000 years during which time they have been born and died in the place of Silas and Amara, who, as true immortals, were invulnerable to any conventional weapon. There are two known doppelgänger lines which stem from Silas and Amara, respectively. Known doppelgängers of Silas are Stefan Salvatore and Tom Avery, and known doppelgängers of Amara areTatia, Katherine Pierce and Elena Gilbert. As of Season Seven, Stefan Salvatore and Elena Gilbert are the last remaining doppelgängers.