Imperial Defence Monitors are dedicated defensive vessels incapable of interstellar travel crewed by Imperial Navy personnel that are designed to engage enemies who are intent on attacking a world or Imperial static installation like a space station. Since such an enemy must approach directly and closely to the planet they intend to assault with ground forces, Defence Monitors do not need much speed or maneuvreability. This allows Defence Monitors to link most of their power generation systems to armaments rather than engines, which often include a massive Lance and a Battleship-caliber weapons battery, granting a Defence Monitor enough firepower to threaten even a capital ship despite it's diminutive size.
- Battlefleet Gothic Rulebook, pg. 144