The Spacing Guild, also known as the Guild of Navigators, or more simply the Guild, was an organization which held exclusive rights to faster than light space travel. The Guild monopoly on space travel and transport and upon interstellar banking is taken as the beginning point of the Imperial Calendar.
Around the Time of the Great Convention
Details of the Guild's emergence are contentious, although it is believed they emerged as a serious political and economic force around the time of The Great Convention.
During the Butlerian Jihad
Prior to this the organization existed as a private corporation, established by the scientist Norma Cenva and her powerful entrepreneur husband Aurelius Venport. When Cenva extended the Holtzman Effect far beyond the scope of its inventor Tio Holtzman, she made possible spacefolding, allowing vast vessels to instantly cross from one point in space-time to another. Prior to this, although described as "outracing photons", vessels still took weeks or months to cross between even the closest stars.
Through the protection and bartering of Venport's company VenKee Enterprises, Cenva's achievement was transformed into a monopoly interest that became essential to the well-being of the post-jihad realm.
During the Corrino Empire
The monopoly of VenKee Enterprises (renamed Venport Holdings) does not last long and is revoked by Jules Corrino, the second Emperor after the Jihad, resulting in numerous competing foldspace companies springing up, like Celestial Transport and EsconTran. However, unlike Venport Holdings, their competition is unable to guarantee safe travel due to the secret to making Navigators remaining with VenHold. Eight decades after the end of the Jihad, Norma Cenva's great-grandson Directeur Josef Venport runs the company with ruthless efficiency, dreaming of taking humanity to new heights of progress. He uses this dream, as well as feeling slighted at his family's monopoly being taken away, to mercilessly crush his competition and even kill rival CEOs. His company continuing to develop new technology and even try to reverse-engineer the technology of the Thinking Machines results in the fanatical Butlerians declaring Venport and his entire company their enemies. During the resulting struggle, which ends up involving House Corrino as well, Venport Holdings ends up turning from the greatest economic power in the Imperium into nothing, as the Butlerians and Emperor Roderick Corrino systematically reduce the company's power and assets. During the Battle of Denali, frustrated at her Navigators being killed during the turmoil, Norma Cenva negotiates with Roderick and agrees to allow Venport Holdings to be destroyed in exchange for the formation of an independent Spacing Guild that would unite the Imperium with safe foldspace travel.
After that, the Guild wields this formidable power during and after the time of Paul Atreides. The Guild was forced to pay a tax to the Imperial throne per flight. This fact brought about the conflict between Earl Dominic Vernius and emperor Elrood IX, because the new Ix-ian highliner design increased the capacity by 18 percent thereby decreasing Imperial income.
Impact of the God-Emperor
New problems for the Spacing Guild created by the ascendancy of Leto II to the title of God Emperor. Leto's extremely long lifespan, coupled with his decision to realize the The Golden Path strategy, saw him hoard the Spice melange with no concern for short-term problems.
Thus, over the many centuries of his rule the Spacing Guild was forced to do his bidding, and their unique powerbase of old was significantly diminished.
While the Spacing Guild remained a powerful body even after the death of Leto Atreides II, their power gradually eroded during the Scattering. By the time of the arrival of the Honored Matres the success of the groups sent out in the Scattering had created new but largely unknown threats to their hegemony. This was because Ixian no-ships, which could perform the most of the same functions of a Guild Navigator, were in common use. As a result, the Guild no longer had a monopoly on space travel.
The Spacing Guild was by its very nature a secretive organization that took up functions previously covered by the Thinking Machines, just as Mentats and the Bene Gesserit did. Their very existence rests on the proprietary knowledge they had clung to for thousands of years.
The inner structure of the Guild during and after the time of Paul Atreides was never fully revealed. However, it is known that the role of Guild Navigator was most prestigious, and the ambition of almost all of those who joined the Guild.
Other known Guild roles included the Chief Administrator, the administrative staff, Navigator attendants, Guild ambassadors, and technical support staff.
The Guild Navigators were utterly dependent on the Spice Melange to safely deliver a vessel via the Holtzman Effect. Even a partial restriction on the Guild's spice requirements rendered them powerless, and reduced long distance trade and transport to a snail's pace.
Prior to the discovery of the Spice Melange's prescient powers, the use of the Spacefolder was very dangerous. One in about every ten Spacefolders was destroyed during travel, because of the lack of a viable method for avoiding gravitational hazards. The safety record was improved in the decades following the end of the Butlerian Jihad even without the use of computers and Navigators by various shipping companies to about 99%, while Venport Holdings (the successor to VenKee Enterprises) had a perfect safety record thanks to the use of Navigators. Seeking to restore his family's monopoly on foldspace travel, Josef Venport hired agents to sabotage his competitors' spacefolders, trying to force them out of business, so that he could seize their assets.