Spanish Inquisition
Unlike their Imperial counterparts, the Spanish Inquisition does not shove Inquisitorial retinues up your ass whenever you commit the slightest of offences. It was however probably inspired by it, or at least, the romanticized version of it, with the grim dark turned up more than a few notches of course.
The real-life Spanish Inquisition were a combined political/religious party formed in 1480 by the Spanish Monarchs Ferdinand II of Aragon and Isabella I of Castile. It was intended to maintain Catholic orthodoxy in their kingdoms and to replace the Medieval Inquisition, which was under Papal control. While the groundwork was laid in AD 1478, the Spanish Inquisition was in power from 1480 to 1834 - 356 years (using 1478).
The Spanish Inquisition is often stated in popular media and medieval history as an example of Catholic intolerance and repression. Modern historians now question or disagree with earlier accounts concerning the severity of the Inquisition. Henry Kamen asserts that the 'myth' of the all-powerful, torture-mad inquisition is largely an invention of nineteenth century Protestant authors with an agenda to discredit the Papacy". Of course it then turned out that 'the Inquisition was a myth' was in fact a myth itself promulgated by those with a pro-religious agenda. For instance it's common to point out that many more people died in WWII, or in 20th Century car accidents, without noting that populations were much lower in the past.
Although records are incomplete, estimates state about 150,000 persons were charged with crimes by the Inquisition and about 3,000 were executed. Defendents had no right to an attorney, no right to see the evidence against them. If they did not confess (and the confession had to include implicating others, who became the Inquisition's next victims), they were subject to torture. Methods included:
Strappado: binding the victims hands behind their back and suspending them by their wrists. Sometimes a series of drops would be added, jerking the victim up and down and forcing their arms out of their sockets. Weights could be added to the victims body to make the hanging even more excrutiating.
Toca, or waterboarding: securing the victim to an inclined board and binding them so that they cannot move. Then the victim is gagged and has a cloth placed over his or her face, and water poured over it. Toca gives the victim a feeling of drowning, even if no water enters the nose or mouth. CIA agents go through it as part of their training and on average last only 14 seconds before begging to be released.
The Rack: often considered the most painful of tortures by contemporaries. The victim had their hands and feet bound to rollers at opposite ends of a frame. The torturer would turn the rollers and the chains attached would dislocate the joints of the victim. If the torturer continued to turn the rollers the victim's arms and legs would be torn off. (Probably not true, tendons and ligaments are incredibly strong. Reports of people being pulled apart by horses mention that they have to be helped by cutting the joints a bit to get the process started. Who knows though, maybe ratchets are just that effective, and some people spent a long time on the rack, which might loosen them up some.)
In an early shout-out to 40k, in 1256, Pope Alexander IV decreed that inquisitors could clear each other from any wrongdoing that they might have performed during torture sessions.
Victoria Lamb makes some pretty badass Spanish Inquisitorial models.
The Spanish Inquisition is not to be expected. ( Despite the fact that they were legally obliged to give thirty days notice. )