Dune: House Corrino:Prelude to Dune Book 3

Fearful of losing his precarious hold on the Golden Lion Throne, Shaddam IV, Emperor of a Million Worlds, has devised a radical scheme to develop an alternative to melange, the addictive spice that binds the Imperium together and that can be found only on the desert world of Dune.

In subterranean labs on the machine planet Ix, cruel Tleilaxu overlords use slaves and prisoners as part of a horrific plan to manufacture a synthetic form of melange known as amal. If amal can supplant the spice from Dune, it will give Shaddam what he seeks: absolute power.