He was guided by a boy, and frequently appeared in Arrakeen to rail against both the Atreides Empire and the environmental changes occurring on the planet. His oratories evoked a variety of emotions from the people of the city, including awe, reverence, anger, and ridicule.
After meeting with Leto Atreides II in the deep desert the Preacher revealed himself to be Paul Atreides, who had been captured by a sietch of rogue Fremen known as Jacarutu when he went out into the desert to die, shortly after the birth of his children and the death of his concubine, Chani.
The Preacher was ultimately assassinated in the main square in Arrakeen, just prior to Leto II taking the throne, with only a handful of individuals (including Leto Atreides II and Gurney Halleck) knowing his true identity. Thus, all that the great Paul Atreides was had become legend.
His message was deep and profoundly rooted in the reality of his day: Muad'Dib was worshiped blindly by the common folk as 'the messiah' of Arrakis and the parasitic Qizarate priesthood took full advantage of this fact. What The Preacher did was to try to awaken his people to the reality of their ignorance, especially since, unknown to most, the "messiah' myth of Arrakis was planted by the Bene Gesserit's Missionaria Protectiva.
"You fool yourselves with images you cannot possibly understand. You cripple yourselves with these toads of ritual and ceremony!" he tells a bewildered audience. This is the essence of his message: the ignorance of the ordinary every-day citizen of Arrakis of having worshiped a man as a god (note that he calls them "idolaters") and the foolishness of submitting blindly to a group of power-hungry, traitorous fools. But it was only after the end of Leto II's reign (and the beginning of the Golden Path) that humanity realized the great extent to which it had been sabotaged for centuries by Bene Gesserit interests, Guild intrigues and disrupted in its enlightenment by petty feuds and individualism.
- Children of Dune (First appearance)