But Matsigenka men do not take the sharing of tobacco lightly. A man’s tobacco is a concrete manifestation of his spiritual powers, and sharing tobacco implies the sharing or transfer of these powers. Indeed, the word for shaman in the Matsigenka language is seripigari, literally, “the one intoxicated by tobacco.”[3] The Matsigenka are circumspect to the point of self-deprecation regarding such matters: no self-respecting shaman would ever openly claim to be one. Instead, those who boast of their shamanic powers are tacitly assumed to be sorcerers, who use spiritual powers for selfish, evil ends.
The most powerful shamans (like the best hunters) are usually the ones who most vehemently deny any such prowess: the Matsigenka universe is a delicate tapestry of reticence, nuance, and insinuation. And yet anyone who regularly consumes tobacco and other psychoactive plants (especially ayahuasca) is, by definition, a shaman, since nicotine intoxication is synonymous with shamanic trance. Shamanism, it would seem, is a matter of degree rather than kind, and although none but the most insecure or inept would openly admit as much, all those involved in sharing tobacco and ayahuasca are scaling the rungs of shamanic initiation. Not even the sky is the limit: the greatest shamans ascend beyond the heavens to mingle with immortal spirit beings, the very gods of creation who defend and perpetuate the universe through their ceaseless war against the forces of chaos and evil.
"The word for shaman in the Matsigenka language is seripigari, literally, 'the one intoxicated by tobacco'.”
As a material substance that stores and transmits spiritual power, tobacco is the shaman’s soul. The more “painful” or “pungent” (katsi) the tobacco, the more powerful the shaman. Nicotine addiction, a physiological reality, also has a spiritual component: The Matsigenka say a man’s shamanic spirit guide craves tobacco the way a hummingbird craves nectar.
http://ethnoground.blogspot.com/2015/06/agony-and-ecstasy-in-amazon-excerpt.html?m=1