"Shogun Warriors" #15 (April 1980) was a fill-in written by Steven Grant with art by Mike Vosburg. The series took a dramatic turn with "Shogun Warriors" #16 (May 1980), as the Shogun Warriors' mentors were destroyed by the Primal One and his followers. This alien force decided that Earth's technology had outpaced its morality, making it their duty to destroy the Shogun Warriors as well as other powerful humans, including Reed Richards and Tony Stark. Declining sales, as well as Moench's commitment to writing the "Moon Knight" comic book series that had just been started, led Marvel to cancel the "Shogun Warriors" comic book series. After Marvel lost the rights to the characters, the Samurai Destroyer (a giant robot built from the pieces of an abandoned fourth robot that was never finished) destroy the other three giant robots off-panel, before encountering the Fantastic Four and the robots' pilots Richard, Genji and Ilongo.