Unbeknownst to the Guild delegation and the rest of the universe, the sandworms on Chapterhouse are not yet producing much melange; the Bene Gesserit are making it seem so, using their own stockpiles.

First the sandtrout, then the worm-all part of the great cycle which had produced melange.

"The information to produce melange from our tanks might induce us to be more liberal with our guest."

Uxtal is ultimately unsuccessful, but the ghola he creates of deceased Tleilaxu Master Waff later offers Edrik something better in exchange for sanctuary - the genetic knowledge for the Guild to create their own, optimized sandworms to produce melange.

Later, the Waff ghola escapes the Bene Gesserit attack on Tleilax, finding refuge with the Spacing Guild by offering Guild Navigator Edrik the genetic knowledge for the Guild to create their own, optimized sandworms to produce melange.

When Guild Navigator Edrik seeks Uxtal's knowledge in producing melange in the tanks, Hellica's price for his expertise is Edrik's help transporting a certain cargo.

Through careful experimentation and development, we believe our axlotl tanks can be modified to produce melange.

Later in the series, an artificial method of producing the spice is discovered by the Bene Tleilax, who develop in secret the technology to produce melange in axlotl tanks.

The Bene Gesserit control the sandworms and their planet, now called Rakis, but the Tleilaxu have also discovered how to synthetically produce melange.