Mauvais Rêves (Bad Dreams) appeared in Pilote in 1967, with the first installment of the story published on 9 November in issue 420, and ran for fifteen issues, concluding in issue 434 on 15 February 1968. Bad Dreams shares an artistic style similar to that of Mézières and Christin's earlier collaborations for Pilote, with influences from Franquin, Morris and Mad magazine artist Jack Davis. Also introduced in this story was Laureline, a peasant girl from the Middle Ages. Originally intended to appear in only one story, the popular reaction to the character meant that she was retained for subsequent stories and she has since become elevated to the main star of the series.Bad Dreams was followed by La Cité des Eaux Mouvantes (The City of Moving Waters) and its sequel Terre en Flammes (Earth in Flames) in 1968 and 1969 respectively. These two stories show some evolution in Mézières' art but also retain the cartoonish influences of Bad Dreams. Jean-Pierre Andrevon best sums up Mézières' style at this time in his 1970 review of the story where he describes Valérian as a "kind of Lucky Luke of space-time". The City of Shifting Waters and Earth in Flames were collected together in one volume in 1970 under the title The City of Shifting Waters. This became the first Valérian album – Bad Dreams was skipped because of its short length – thirty pages – relative to the usual album length of around 46 pages. Every Valérian story up to and including The Rage of Hypsis in 1985 would debut in serial form in Pilote before being published as an album.L'Empire des Mille Planètes (Empire of a Thousand Planets) premiered in Pilote in 1969 and marked a further development for the Valérian series and for Mézières art. This story was the series' first full-blown attempt at space opera and it set out for the first time the two main signature elements of Valérian: the use of science fiction as a political allegory and Mézières' meticulously detailed depictions of alien worlds. The follow-up story World Without Stars saw the final evolution of Mézières' art into the style that became prevalent in the Valerian stories of the 1970s and 1980s, with the first realistic renderings of Valérian and Laureline, as opposed to the caricatures of the earlier stories.Valérian is Mézières' best-known work, translated into at least thirteen languages: the last album, L'Ouvre Temps, was