Since 3.9, if you take the quest to clear a village being ravaged by bandits, Rogue Blackheart Knights and Squires can appear leading those bandits.
These less than honourable knights can often be found in the prisoner trains of defeated lords, and due to their level, they can be recruited when rescued or when becoming your prisoners through the camp recruiting option. Often they spawn with Hawkstorm Bows, Ebon Bows, or Short Composite Bows, always with Bodkin Arrows, so decide carefully whether or not you consider them horse archers or heavy cavalry. They are skilled with these bows, and can be very useful in sieges. In melee they can spawn with Runed Bastard Swords, one of the best weapons in Pendor. They ride either Imperial Silver Stallion or Netherworld Charger. All of this makes these knights one of the best-equipped units in Pendor.
Overall, they are a well-rounded unit that will combine well with any army. You may consider them a lower-cost alternative to the Hero Adventurer that is easier to obtain.
They are also known as Pendor Rogue Knights. Perhaps they are the nobles descended from the Old Kingdom of Pendor?
This troop is upgraded from Rogue Blackheart Squire for 80 d and upgrades no more.