Suk doctor Wellington Yueh, the Bene Gesserit Lady Jessica and Harkonnen enemies Duncan Idaho and Gurney Halleck ally themselves with Leto, and Shaddam nearly destroys the all-important planet Arrakis thinking he has found a replacement for its priceless and essential export, melange.
"Dune: A Whisper of Caladan Seas" takes place during the Harkonnen attack on Arrakis during the course of the original Dune by Frank Herbert.
The Emperor's power derives from Imperial control of the seemingly invincible military forces of the Sardaukar, and of the planet Arrakis and its priceless melange, a source of endless wealth.