Imperial Security Organization

ISO can be safely considered a splinter organization of early Brotherhood of Crows. It was created following Dawn War with assumption that Grand Emperors should have a separate intelligence organization – one apart the Brotherhood, whose loyalty lies in Imperium rather in its current leadership. Such is how ISO was created.
It is organization dedicated mostly to counterintelligence and internal security, supposed to monitor activity of other imperial organizations (especially Imperial Temple and Imperial Magic Guild) and at least the notable vassal states, which is achieved by a vast ammount of methods, from simply listening to what people whisper to each other during parties to gaining personal informants. With occasional breaking and entering.
Unlike Brotherhood of Crows it isn't an organization of zealot patriots fully capable to kill even the Emperor if they think his death will benefit Imperium, but a group of well paid professionals. Different approach to their work, different approach to murder as a method, the same (more or less) mission. No wonder they both dislike each other and tend to rival quite fervently.

Structure

Structures of ISO are more or less typical for imperial organizations. Local headquarters in provincional capitals (at least those with local countries that can potentially become a threat to Imperium of Karadia, central headquarters in Falon-nir. Its head is titled Imperial Spymaster and his... power is quite expansive, with one or two becoming successful usurpers.
It is considered an organization belonging personally to the Grand Emperors, but it is governed by the Imperial Ministry of Internal Affairs and financed via this organization.

Public Agenda

Plain old intelligence gathering. They are needed so that Imperium will know if there are problems brewing in vassal states or if for example several army generals are plotting something spectacular.
This makes them a group similar to Brotherhood of Crows that is, however, notoriously unreliable and fully ready to actually silently let the schemers push their plot forward if they think that changing the leadership will benefit the Imperium. ISO was mostly created to counter their influence.
There were even several semiopen clashes, always silent but always with lots of people dissapearing and other turning out drifting down the rivers. Which likes to happen especially when current Imperator turns out to be a megalomaniac madman, and Brotherhood wishes to have him dead.

Type

Information Network