A starship launched missile, created by the Thinking Machines; which once launched, would create a fiery blast of immense heat, destroying everything in its’ path.
Destruction of Rakis
In Heretics of Dune, by Frank Herbert, it is learned that Obliterators were first used by Honored Matres in their major attack against Rakis, in their successful attempt to kill Supreme Bashar Miles Teg. Because Teg had killed some of the Matres’ leadership earlier in the year while on the planet Gammu; Teg, the Bene Gesserit Mother Superior Alma Mavis Taraza, and the Tleilaxu Master Scytale knew that a retributive strike would come. With Sheeana, who gathered a sandworm from the surface of Dune, Taraza's assistant Darwi Odrade and Scytale fled the surface of Rakis, just before the Matres arrived. Teg stayed behind on Rakis to ensure the prior group’s escape.
When the Matres struck Dune with the Obliterator missiles, the atmosphere immediately caught fire, which caused half of it to evaporate. The immense fireballs scorched the surface of the planet killing almost all life on the world, sandworms and humans alike, including Teg. Much of the sand on the covering of the planet, when exposed to the extreme heat of the Obliterators, fused into a type of hardened glass.
Matres Acquistion of Obliterators
In Hunters of Dune, by Brian Herbert and Kevin J Anderson, it was found out by Murbella, leader of the now combined Matres/Gesserit New Sisterhood, 32 years after the destruction of Rakis, how the Honored Matres initially acquired the Obliterator weapon. While under the influence of a large dose of melange, Murbella accessed previously hidden portions of her Other Memory. She learned that the Matres in their expansion centuries earlier during The Scattering, had stumbled upon a remote outpost of the Thinking Machine empire in deep space. The Matres had stolen a multitude of Obliterators from the outpost, and used the weapon itself to destroy the machine station.
When word of the attack reached Omnius, leader of the Machines, he immediately launched a counter-attack against the Matres with both ships and the Omnius Scourge, the deadly plague. This caused the Matres to immediately retreat and bound their way forcibly back into the Old Imperium, with the stolen Obliterators as their doomsday weapon.
Destruction of Richese
Murbella knew that the only chance humanity stood against Omnius’ soon-to-be-coming Thinking Machine space armada, was the Obliterator weapon. She commissioned the building of Obliterator weapons at both starship production yards located at both Richese and Ix.
A few years later, the rebel Matres leader Hellica, decided a show of force against Murbella. Hellica knew that Murbella had contracted with Richese to produce starships and the super-weapons for the Sisterhood. Hellica enticed the Guild Navigator Edrik to transport her fleet and Obliterator weapons to Richese, fired her Obliterators, and reduced Richese and its’ surrounding production yards to slag.
Preparing for Kralizec and Above Chapterhouse
In Sandworms of Dune, by Brian Herbert and Kevin J Anderson, it was learned that a few years later, that the Ix production crew of the Obliterators had secretly been killed by, and replaced by Enhanced Face Dancers, who had subverted the building of the super-weapons. As the end of the age came near, the sabotaged Obliterator weapons were loaded onto starships in a last ditch stand when the Machine armada reached humanity’s “line in the sand” above Junction and the planet Chapterhouse. Murbella’s and the Sisterhood’s plan went awry when all of the Obliterator weapons malfunctioned when fired, and that humanity could not stop the Machines.
The super-weapons were not needed, as the Oracle of Time appeared with her Navigator Heighliner fleet, and destroyed the first wave of the Machine armada. The second wave of the armada went off-line as the Oracle subsequently banished Omnius to another universe; and the now-revealed Ultimate Kwisatz Haderach Duncan Idaho, became the new Evermind, and ended the conflict.