The Chaos Styx-class Heavy Cruiser was used throughout the Segmentum Obscurus and in many Imperial Navy fleets of the Ultima Segmentum during the 32nd and 33rd Millennia. In most fleets they were later phased out, in favour of the new Mars-class Battlecruiser that was created with its deadly Nova Cannon armament. With the advent of the newer Cruisers, many of the old Heavy Cruisers were given less and less attention for refits and rearming. This led to a number of captains denouncing the Imperium and turning Renegade. In the Gothic War the Styx-class was essential for the followers of Abaddon in many battles, as its considerable flight bays can house and launch almost as many Attack Craft as an Emperor-class Battleship. Particularly during several planetary assaults, bombers from Styx-class Heavy Cruisers were used for destroying ground-based defences before larger vessels and troop transports entered low orbit.
Mustering a considerable array of long-range weapons batteries to complement its sizeable launch bays, the Styx is even more formidable than its considerable tonnage would suggest. There are 7 recorded instances of Styx-class Heavy Cruisers fighting against the forces of the Emperor in the Segmentum Obscurus before the Gothic War. During that conflict, this figure rose to 39 major fleet battles involving Styx-class ships, demonstrating the value the followers of the Dark Gods placed on their capabilities. Although there were at least 5 ships of this class ranged against the Imperium during that campaign only two were identifiable: the Horrific and the Heartless Destroyer. Both had been laid down in the Cypra Mundi orbital dockyards in the early 33rd Millennium, and the Heartless Destroyer and the Horrific were frequently found in action together in various Chaos fleets. In 299.M35 the Heartless Destroyer, the older of the two vessels, withdrew from an engagement against Traitorous raiders, leaving its companion ship to be reduced to a hulk and captured. Until their reappearance during the Gothic War, there had been no more reports of either ship. Certain incidents where the two vessels fought together indicated there was still a great deal of enmity between them and in the Battle for Duran, the Horrific repaid the earlier treachery of its companion vessel. It abandoned the Chaos warfleet it had been a part of during the final assault of that battle and the Heartless Destroyer was crippled. The badly mauled Heavy Cruiser was then eventually destroyed when it drifted into range of the Imperial planetary defense platforms.
Notable Styx-class Grand Cruisers
- Heartless Destroyer
- Lord Seth - The Lord Seth fought during the Gothic War. It was the flagship of the Chaos invasion fleet that assaulted the planet of Helia IV, and it was ultimately destroyed by repeated torpedo strikes from taht world's Imperial defenders.
- Pluton - The Pluton fought during the Gothic War. It was sighted at the Battle of Helia IV but escaped Imperial retribution and fled to harass the the servants of the Emperor another day.
- Scylla - The Scylla fought during the Gothic War. It was one of the many vessels who escorted Abaddon the Despoiler's Planet Killer wherever it went, tasked with protecting the doomsday weapon from any attack.
- Hull: Heavy Cruiser
- Class: Chaos Styx-class Light Cruiser
- Cross Ref: Blasphemy/Treachery/Heresy/Abomination
- Security Rating: Epsilon Primus
- Threat Rating: Alpha Majoris
- Classification: Maximus
- Current Location: Unknown
- Current Status: Active
- Recommended Response: Damnatus. Expurgatio in Extremis
- Battlefleet Gothic (Blue Book), p. 120
- Execution Hour (Novel) by Gordon Rennie