The Eisenstein was an Imperial warship that played a crucial role at the outbreak of the Horus Heresy, carrying loyalist Space Marines back to Terra from the Isstvan System, to warn the Emperor of Horus' treachery.
The loyalist legionaries were referred to as The Seventy.
The Eisenstein was considered an old craft even by the time of the Heresy. At over 2 kilometers long and resembling a Gladius Class Frigate, the Eisenstein was in service to the Death Guard by the events on Isstvan III. According to the Eisensteins captain, in an ancient Earth language, "Eisenstein" means "iron-stone", and was the name of two noted men from the Age of Terra - one a remembrancer, the other a scientist.[1e]
Shortly before the massacre at Isstvan III, Nathaniel Garro and his Company were assigned to the Eisenstein. Because of an injury suffered in a recent skirmish, Garro was prevented from joining the surface attack with the other Death Guards. First Captain Calas Typhon stationed Ignatius Grulgor's company aboard the Eisenstein to deal with Garro and his men when the time came[1a]. As was typical of Astartes ships, day-to-day operations were overseen by a Human crew, in the Eisenstein's case this was under Shipmaster Baryk Carya. Before the bombardment started, Saul Tarvitz transmitted a warning to the Eisenstein, before flying down to the planet's surface to attempt to warn the other loyalists. Acting on this warning, Garro and his men investigated the rest of the ship and found Grulgor and his men preparing to bombard the surface with virus bombs. Garro attempted to stop it, and one of the bombs ruptured, killing Grulgor and his men[1b].
Shortly before taking the Eisenstein to warp, to travel to Terra and warn the Emperor, Garro was joined by Iacton Qruze and a group of civilians escaping from Horus's flagship, at the direction of Garviel Loken. The Eisenstein narrowly evaded fire from Typhon's ship, the Terminus Est, before escaping the system[1c].
During its voyage, the ship's Geller field failed briefly, allowing the power of Nurgle to re-animate the corpses of the dead Marines, who were unstoppable until Garro ordered the ship to make an emergency reversion to the Materium. The tainted Marines disappeared, but the stress of the reversion was too much for the ship's Navigator. The Eisenstein was stranded, until Garro ordered the ship to jettison its warp engines and detonate them, in the hope of signalling a passing ship. They were rescued by the Imperial Fists' mobile fortress monastery, the Phalanx, and the Eisenstein was scuttled[1d].
Since the Heresy, the Eisenstein has garnered a mysterious reputation and its status remains unclear. Sometime after the formation of the Great Rift, many saw the vessel reappearing on multiple occasions. On the seventh such appearance, it is said that Mortarion himself will appear and wreak destruction.
Crew at the time of the Heresy
- Baryk Carya — Shipmaster
- Racel Vought — Executive Officer
- Tirin Maas — Vox officer
- Severnaya — Navigator
The Eisenstein was originally created for the 1988 Realm of Chaos "Slaves to Darkness" book, published for the First Edition of Warhammer 40,000 in order to introduce the Horus Heresy. The one-paragraph mention describes how "loyal Adeptus Astartes officers and troops" took over a frigate named Eisenstein after they discovered Horus's Chaos taint at the time of Isstvan III being bioweapon bombarded. The ship was reported to flee to warn others as Horus moved to Isstvan V.
The 1989 game "Space Marine", precursor to the Epic game system and takes place during the Heresy, describes the Eisenstein in a story box through the conversation of Captains Tarvitz, Garro, Varren, and unnamed others. Their topic was to either "Betray Horus or betray the Emperor," and in it we are told that Horus had five "Chapters", incorporated warrior-lodges from Davin within them, and the Codex command structures were disregarded. Additionally, the "bulk" of the legionaries under Horus were now loyal to "feral world deities" and to Horus. Istvaan (alternate spelling in early texts) was destroyed without order from Terra, and the virus bombing was not justified. 
There is no mention of loyalists being killed. Captain Varren says that he has 15 men of the World Eaters, Captain Garro says 12, an unnamed voice says 10 from the Luna Wolves, and another unnamed voice says 20 from the Thousand Sons. Tarvitz says that there are 9 Emperor's Children beyond himself. In total, it represented 70. They agree that Varren will take the frigate Eisenstein because it is able to warp jump, and Tarvitz mentions that it was falling behind because of mechanical problems. The others would slow their own ships and then take control of the five ships. Four of the ships would then defend the Eisenstein and clear a path for it to flee. The World Eaters under Varren would then take the message.
In one source, the exact number of Marines from each Legion that escaped to warn the Imperium were[Needs Citation]:
- 13 Death Guard (Led by Garro)
- 14 World Eaters (Possibly including Varren)
- 11 Sons of Horus
- 21 Thousand Sons
- 11 Emperor's Children
Other sources[Needs Citation] state that the 70 marines were lead by Captain Varren of the World Eaters, and escaped in Thunderhawk transports.
Still another source[Needs Citation] suggests that Captain Saul Tarvitz of the Emperor's Children led the group. According to this account, Varren's World Eaters were supposed to seize control of the Eisenstein at the same time that the other Marines would take control of four separate ships (presumably their own transports/frigates) and use these vessels to defend the Eisenstein so it could jump to warp space. This does not mesh with later sources, which seem to imply that all 70 Marines were aboard the Eisenstein on its voyage to Terra
This account also presents a slightly different number or Marines per Legion[Needs Citation]:
- 16 World Eaters (Including Varren)
- 13 Death Guard (Including Garro)[Needs Citation]
- 10 Luna Wolves[Needs Citation]
- 20 Thousand Sons
- 10 Emperor's Children (Including Tarvitz)
Unfortunately this adds up to only 69 men. It is possible that one of the unnamed officers of either the Luna Wolves/Sons of Horus or Thousand Sons included themselves in the count and the other didn't, since the numbers appear as direct quotes from the officers in question. Of course, there is no way Varren, who remarks in the source that the total of seventy Marines is equal to the sum of the five Legions' Numbers, could know this. It is thus probably a simple mistake in the text.
Each of these accounts cause problems. The original account introduces the Inquisition at the time of the Emperor. Gav Thorpe has since changed the creation of the Inquisition to after the Emperor's Ascension for the Inquisitor game.
According to The Flight of the Eisenstein, all the Marines aboard the Eisenstein are Death Guards, except for Iacton Qruze; Varren does not appear, while Tarvitz attempts to reach the planet's surface rather than escaping aboard the ship.
In the audio drama Garro: Sword of Truth, loyalist elements of the Emperor's Children and the World Eaters (including Varren) flee the Isstvan system at the same time, and reach Terra shortly after Garro returns from his mission to Calth.
- 1: The Flight of the Eisenstein (Novel)
- 1a: [Needs Citation]
- 1b: [Needs Citation]
- 1c: [Needs Citation]
- 1d: [Needs Citation]
- 1e: [Needs Citation], pg. 168
- 2: Garro: Sword of Truth (Audio Book)
- 3: Codex: Chaos Space Marines (4th Edition)[Needs Citation]
- 4: Realm of Chaos "Slaves to Darkness" pg. 240
- 5: Space Marine (Game), 1989 edition, pg. 7.
- 6: Codex: Death Guard (8th Edition), pg. 22