The Thule Society
The Thule Society on wikipedia
Founded in 1918 by Rudolf von Sebottendorff, the Thule Society is a German folk movement, intent on establishing a shared history and heritage for its members. First mentioned by the Greek writer Pytheas in the 4th century BC, Thule was supposedly a island paradise far to the north of Scandinavia; a sort of Germanic Atlantis. The society that takes its name is dedicated to founding such a paradise on earth, ruled by the society's elite, noble founders, of course.
Though not without secret military might, the Thule Society is mostly an occult secret society, engaged in expeditions the world over to recover artifacts of power for use in their struggle. Amongst their tenets is that the earth is hollow, that a mystic energy called vril permeates the world, waiting to be harnessed, and that great men (like Aryan Germans) are descended from a powerful precursor race of people, called Hyperboreans. Much of this thinking is based on the Theosophical philosophies of Helena Blavatsky who was, herself, strongly influenced by Hindu yogic mysticism.
Doctor Joseph Dippel is one of their leaders and Rheinholdt Dietrich seems to be one of their chief operatives.