Mystery cult and religion of salvation, Mithraism represents the regenerative sacrifice of the Indo-European world, the Zoroastrian doctrine of the struggle between light and darkness and the final regeneration of the world. From India to the Atlantic, the developments and changes of an Indo-European sovereign and savior God who has had faithful for millennia, studied from a historical and phenomenological point of view. Mithra is a sovereign god of the Indo-Iranian world whose cult, which arose in India, passed to Iran and then to Commagene and at the beginning of the Christian era he conquered Rome, where he placed himself as a rival of the religion of Christ. In this volume, Julien Ries follows in his footsteps from India to the shores of the Atlantic. With a particular insistence on doctrines and on the repercussions they have had on society and on the life of the faithful, he draws a synthesis that, starting from the Vedic religion, crosses ancient Iran, considers the royal and public worship in Commagene and ends with the Mithraic mysteries widespread in the Roman Empire. What emerges is a vivid, effective and complete picture of the historical peculiarities and changes of the cults of a god who, while retaining numerous traits of his primary identity, under the influence of the cultural and religious elements encountered on the paths of his migration, suffered the effects of acculturation and syncretism.