Slud is an Imperial Feudal World and Mining World governed by rulers who received payments for the rare metal deposits mined from the world. Its people are essentially used as slaves by the governing class. The Imperium believed that it was best for the natives' productivity if they remained blissfully unaware of the wider galaxy. As such, it limited their exposure to advanced technology.
At some point in the 41st Millennium, the Planetary Governor Dartsma Ret chose to dramatically increase the price he charged the Imperium for his world's ores. It was then that Imperial authorities decided to replace him with a more cooperative puppet.
The Imperium sent a squad of Space Marines to remove Ret, but ordered them not use advanced technology or their normal wargear to maintain the Sluddite populace's ignorance. As a result, the Astartes were forced to wield only pre-industrial armour and weapons equivalent to that used during Old Earth's European Middle Ages.
Sources[]
- Warhammer: Siege (1st Edition), pg. 94