The battlecruiser concept arose as a result of the perceived failures of the older grand cruiser designs. These had been built around advanced experimental drive systems, which ultimately proved to be unacceptably prone to catastrophic malfunction during warp transit. As a result of these issues, grand cruisers came to be regarded by many as cursed ships. Furthermore, during the internecine conflict of the Age of Apostasy, several of the skills required to safely maintain the arcane technologies of the grand cruisers were lost, rendering them hazardous.
Yet there was still a gap in the Imperial armory for a heavy cruiser, a vessel which straddled the gap between a “classic” cruiser like the Lunar class and a full battleship. Numerous small task forces required a powerful flagship, yet the potent and precious battleships could not be spared for every such engagement.
User the simpler technologies of the latter Imperial cruisers, and the power systems of battleships, the master tech-masons of the Adeptus Mechanicus produced and elegant hybrid, the battlecruiser, during the latter 36th Millenium. Designed to provide the fleet with the long range punch of battleship weaponry in a cruiser-sized hull, battlecruisers are forged purely for heavy engagements between vast capital vessels, and excel in this narrow specialty. They overpower cruisers by virtue of their overcharged weaponry; very few ships can out-shoot a battlecruiser.
Typically somewhat smaller and more lightly armored than their predecessors, the grand cruisers, battlecruisers are nevertheless more economical, safer and more reliable. What they lack in heavy armor and exotic drive systems is more than made up for in raw firepower. Jealously guarded by battlefleet admirals, it is rare for these powerful ships to end up in the ragtag Rogue Trader fleets, but on occasion a particularly influential or devious individual will intrigue his way into the command of a battlecruiser.
As follows are the varied battlecruiser-class hull types available in the Koronus Expanse and Calixis sector. Note these hull types consist of Imperial-pattern starships, and equivalent xeno or chaos pattern hulls may vary considerably.