From 2004 to 2008, Cassaday illustrated the graphic novel trilogy "Je suis légion" by from Les Humanoïdes Associés. The English language edition was published as an eight issue comic series "I Am Legion" by Devil's Due Publishing. In July 2006, Humanoïdes announced a co-production deal with Pierre Spengler for a screen adaptation of the work. At the 2015 Cannes Film Festival, it was announced that the three picture series would be directed by Nacho Cerda with a screenplay by Richard Stanley.