Agartha

The concept was introduced by Louis Jacolliot in his 1873 book Les Fils du Dieu, and was expanded upon by authors Alexandre Saint-Yves d'Alveydre, Ferdynand Ossendowski and René Guénon.

[6] Notoriously Solar Temple members ended up committing mass murder-suicide throughout the 1990s, partially rationalizing this as completing the "cycle" started by the Grand Lodge of Agartha.

"[3] Agartha's origins can be traced back to Victorian attempts to interpret mythology through a euhemerist lense, seeing them as containing references to hidden past history; due to influence from the racist theories at the time, this was usually taken from ancient Germanic myths.

Jacolliot was a colonial official in South India, and a writer of many popular books, including a trilogy discussing Indian mythology's relationship to Christianity.

[10][3] In this book, one of the trilogy, he claimed that he had been given access to ancient manuscripts that revealed 15,000 years of Indian history by Brahmin friends of his in Chandernagore, who had told him the story of 'Asgartha'.

[3] Three years after the publication of Jacolliot's book, an anonymous piece of literature called Ghostland, or Researches into the Mysteries of Occultism, was published, discussing Agartha.

[3] In his 1922 book, Beasts, Men and Gods, the Polish explorer Ferdynand Ossendowski relates a story which was imparted to him concerning a subterranean kingdom existing inside the Earth.