In 1981's God Emperor of Dune, Leto Atreides II talks about his relationship with the former Ixian ambassador Malky, who had been specially raised and trained by the Ixians to be a "tempter" — the "Devil to Leto's God". The Ixians had intended for Malky to manipulate Leto into doubting his own purpose; the plan had ultimately failed. They had later created Hwi Noree, a female designed specifically to attract, seduce and hold influence over Leto. In the novel, Leto meets Hwi and sees this intent, but cannot dismiss his attraction to her. The Ixians have an embassy on Arrakis which is infiltrated by Tleilaxu Face Dancers, who kill and replace everyone there — except for Hwi — as part of an assassination attempt on Leto. The attempt fails, but Leto later allows himself to be killed by Siona Atreides, as part of his own plan for the universe.
The Ixians had managed to keep Hwi's development a secret through the use of their new invention, the no-chamber, which contains machines that hide the people within from prescience (as Guild Navigators can do). They had also created the Navigation Device which would eventually take the place of Guild Navigators and help fuel The Scattering. Combining these two technologies later results in the no-ship, a starship that can remain unseen and does not require a Navigator to fold space.
By the time of Heretics of Dune (1984), the power of the Ixians seems at its apex with their alliance with the Fish Speakers; however, Bene Gesserit analysts see them as a failing power, because Ixian society had become a bureaucracy and no great inventions had come out of the workshops of Ix for centuries. When the Honored Matres conquer the Old Empire, the Ixians are reduced to a barely tolerated technological combine.
House Vernius rules the planet, but the Padishah Emperor Elrood Corrino IX holds a grudge against Earl Dominic Vernius for two reasons: Dominic had married Elrood's former concubine, Shando Balut, and Ix's new, larger heighliners negatively impact Imperial tax revenue on cargo.
Elrood secretly grants the Tleilaxu the right to occupy Ix by force (with the help of his Sardaukar army) and remake it into a laboratory station for Project Amal. This secret project seeks to produce a synthetic version of melange the Tleilaxu Master Ajidica calls ajidamal, or amal. The old Emperor wants to remove the spice monopoly by making sure that he has the only access to it, thus controlling the Spacing Guild. The Tleilaxu rename Ix "Xuttuh" after their founder. In the year 10,156 A.G., Elrood IX is assassinated by Count Hasimir Fenring. Crown Prince Shaddam, now under the name of Shaddam IV, gives Fenring the title of Imperial Spice Minister and orders him to supervise the project.
Although Ajidica manages to create an artificial melange that seems to have the original's properties, it does not work properly. The test-sandtrout explode, and Fenring's test of its use on two Guild Navigators ends in catastrophe. When Duke Leto Atreides invades Xuttuh in 10,175 A.G. and reestablishes Prince Rhombur of House Vernius as the ruler of Ix, all the records of Project Amal are destroyed.
In the War of Assassins, the Ixians now play a more direct role in combat, interacting with the three Houses as trading partners. An alliance with House Ix can be forged by aiding them in various missions, providing that the player doesn't ally with the Tleilaxu first, as the two are bitter enemies.
Once allied, the Ixians will provide the player with units built from the House of Ix. These include the Infiltrator (a stealthed mobile kamikaze unit that reveals cloaked enemy units when it detonates), and the Projector Tank (fast hover tank with light mounted cannon, which when deployed, is able to project holographic images of the player's troops that provides realistic damage, yet disintegrates harmlessly on impact).
The Ixians have also been known to be victims of the Bene Tleilax forces on Arrakis, having dead Ixians harvested for use in their Flesh Vats. There is also a mission involving a revolt of the lower class on an Ixian research facility that parallels the revolution mentioned in Dune: House Atreides (1999).