By melding with an immaterial and atemporal substance which is the source of all power and knowledge, Achuar shamans act as if they are continually reenacting the conditions described in the primordial myth, when society came into being. Using a comparative approach to unpack this logic, I will concentrate on the role and nature of essential substances and how these consolidate the ties between shamans and their allies in South America. Inspired by comments made by Bernard Saladin d’Anglure when he discussed ‘mythic allies’, I will examine how these immaterial substances define the quintessence of being human and shape ethnicity and shamans’ powers.