 Cadogan studied, published and became an authority on Mbyá Guaraní, Ava-Guaraní, Pai-tavytera, and Ache-guayaki — various Guaraní tribes living in the forests of eastern Paraguay.Cadogan was accepted as a member of the Mbya-Guaraní and initiated under the spiritual name of "Tupa Kuchubi Veve" ("One who flies like a whirlwind").The Mbya-Guarani had a secret, esoteric religious language unknown to the world until his initiation.