The capital world of the Saedran Sub-sector and the Eridani Sector as a whole, Saedra is situated on a warp route that connects the Achernar Sector, the Graiae and the spinward reaches of the Saedran sub-sector with the wider Imperium. This makes it a trading hub of significant strategic value, and consequently it is well defended by orbitals, system ships, and a substantial planetary defence force. There are two inhabited worlds in the system: Saedra IV and Saedra VII.
Eridani's capital world is a formidable bastion orbited by two Ramilies-class star forts and a range of other orbital and surface defence platforms. As a planet situated on a major trade route, there are vast orbital warehouses where cargo modules are dropped off and collected by the ships performing that leg of the journey. Naturally this has led to Saedra IV being the place where many deals are struck; a ship might arrive with goods and start looking to strike up a contract or one-off sale with one of the great trading brokers, who over the centuries have grown extremely influential, to the extent that some joke it's better to be hounded by an Inquisitor than a Saedran Broker. Untrue, of course, but indicative of their preeminence in the Eridani Sector.
Arguably just as vital as the capital world, Saedra VII is a planet given over to the Adeptus Mechanicus and is very nearly a Forge World in its own right. Referred to simply as 'Seven' by its Technocratic overseers, it is home to the largest shipyards in the Eridani Sector, and has a copy of the STC templates needed to build Ramillies-class Star Forts. That it has three sat in orbit is a source of some contention with the governor of Saedra IV, given that they only have two. This disagreement is regarded by every other planet in the Sector as possibly the most privileged argument ever embarked upon, given the near-total lack of such star forts anywhere else in the sector. Most of the star forts produced by Seven are moved to other, more embattled sectors of the Imperium.
Beyond gargantuan space stations, Seven also manufactures a wide variety of ships, military equipment, and civilian machinery. Given the unacceptable strategic consequences of losing Seven to an invasion, the Divisio Militaris of the Collegia Titanica regularly stations at least one maniple of Titans on the planet. As Eridani is historically a relatively quiet sector, this is usually used as an opportunity for high-level maintenance of the god-machines.