Such a vessel is flown into the heart of an enemy fleet by a skeleton crew who then evacuate in escape pods before detonating the ship -- though it is not uncommon for the crew to stay at their posts to the bitter end to ensure that they cause the maximum possible damage.
The large explosion caused by detonating a Fire Ship will pass through other starships' shielding to set the hulls of any nearby vessels ablaze, instantly destroying escorts and badly damaging even large capital ships.
This deadliness was aptly demonstrated at the defence of Delos, the very first battle in which Fire Ships were used during the Gothic War, when Commodore Kurtz used two such vessels to cripple the Chaos Devastation-class Cruiser Unforgivable.
- Praetorian of Dorn (Novel) by Chris Wraight
- Battlefleet Gothic Resources: Ships of the Gothic Sector, pg.143