A battle cruiser is a specifc variant of the Defender Class Starship that provides tactical support to Exploring Expeditions. The Permanent Saphire Defense Office contracted with the Hyperion Battleship Alliance (a consortium of Sapphirean companies) to develop and build a larger and more potent Defender with upgraded armor and weapons systems. Although they may support StarForce operations, these ships operate specifically under Sapphirean Flag and Sumacian command and operational protocols. In addition to combat operations, they also support of Exploring Expeditions sponsored by the Free Worlds when traveling into unknown and potentially hostile areas of the galaxy.
The PSDS makes it a point to give these ships names intended to threaten and intimidate adversaries. Known examples of the type include:
- Skullcrusher -- The ship to which Blade and Hardcandy Banks Toto transferred in Book 11 - Charlemagne. Skullcrusher was part of a seven-ship Exploring Expedition into the uncharted Carinae Quadrant. ("You should have heard the name they originally wanted. It wasn't Skullcrusher if you know what I mean and I think that you do.")