The Signus Campaign

The Diversion

Horus, having committed to the Heresy, faced a strategic problem: the Blood Angels were among the loyalist Legions most capable of breaking his early offensive. The Sanguine bloodline was disciplined, fast, and personally led by a primarch (Sanguinius) whose tactical instincts Horus knew first-hand.

Horus's solution was the Signus diversion. He arranged for the Imperial Senate to redirect the Blood Angels to the Signus cluster — a fringe region that had reportedly fallen to a daemonic infestation — to ostensibly suppress the threat before it spread. The cluster's infestation was real. It was also far worse than the briefing indicated.

The Trap

The Signus cluster contained the gathered daemon-hosts of all four Chaos Gods — assembled specifically to trap and consume the Blood Angels. Khorne sent his Bloodthirsters. Tzeentch sent his Lords of Change. Nurgle sent his Plaguebearers in tides. Slaanesh sent her Keepers of Secrets. The Blood Angels descended into a system that should have, by every projection, killed them entirely.

The trap nearly worked. The Blood Angels lost battle-brothers in numbers the Legion had never previously absorbed in a single engagement.

I am Sanguinius. I am the Angel. Stand up.

— Sanguinius, attributed Signus Prime

The Duel

The trap's centrepiece was a duel between Sanguinius and Ka'Bandha — the Bloodthirster commanding Khorne's contribution. The duel took place on Signus Prime, the cluster's key world, before a battlefield of watching daemons and Astartes.

Ka'Bandha broke Sanguinius's back with a single strike. The primarch should have fallen. He did not. He stood back up, his spine reconnecting through whatever combination of Sanguinary physiology and primarch-grade willpower he commanded, and defeated Ka'Bandha in single combat anyway. The Bloodthirster was banished.

The rest of the daemon-host broke. The Blood Angels held the cluster.

Aftermath

Signus changed Sanguinius. The Blood Angels' gene-seed instability — the Red Thirst, and the deeper Black Rage that would manifest after his death — appears to date from the Signus engagement. The campaign also gave Sanguinius prophetic clarity about his own eventual death; he saw Horus, in some sense, for the first time.

The Blood Angels marched from Signus directly to Terra. They arrived in time for the Siege.

The Trap Specifics

The Signus Campaign was a arrangements that Horus had designed to incapacitate the Blood Angels Legion before the Legion's expected operational arrival at Terra for the Siege. The campaign's mechanism involved Horus's orders to Sanguinius personally — orders that directed the Blood Angels Legion to engage what the orders specified as a xenos threat at the Signus Cluster, when in operational reality the cluster's arrangements had been engineered by Horus's specific Heresy-aligned subordinates into a sustained Khornate ritual-engagement zone.

The Blood Angels Legion's arrival at Signus in 005.M31 produced the engagement that Horus had anticipated. The cluster's arrangements engaged the Blood Angels Legion in sustained Khornate ritual-combat across approximately seven Terran weeks; the engagement's consequences consumed approximately 30% of the Blood Angels Legion's pre-Signus operational strength.

Ka'Bandha's Engagement

Ka'Bandha — the Khornate Bloodthirster classified as the engagement's senior daemonic operational arrangement — personally engaged Sanguinius in combat during the campaign's operational climax. The engagement's outcomes were significant. Sanguinius injured Ka'Bandha during the engagement; Ka'Bandha injured Sanguinius during the engagement; neither killed the other.

The consequences of the engagement on Sanguinius's arrangements were sustained. Sanguinius's injuries from the Signus engagement degraded his capability across the subsequent Heresy-era operational arrangements; the degradation contributed to the outcomes of the Siege of Terra's specific final engagement. Ka'Bandha's arrangements post-Signus has been sustained-personal-hostility toward the Blood Angels Legion's arrangements across the post-Heresy era.

The Sanguinor Manifestation

The Sanguinor — a arrangement that the Blood Angels Legion classified as Sanguinius's angelic manifestation — appeared during the campaign's final operational phase. The Sanguinor's properties have been the subject of approximately seventeen Imperial Cult classified internal investigations across the post-Heresy era. The investigations have produced inconsistent results; the most-cited working hypothesis is that the Sanguinor is a manifestation of Sanguinius's specific personal disposition that engages during the Legion's arrangements of greatest institutional need.

The Sanguinor's arrangements has continued across the post-Heresy era. The manifestation has been observed in approximately seventy-three documented Blood Angels Legion operational arrangements since Signus; the manifestations' arrangements have been consistent across the documented observations. The Blood Angels Legion's position is that the Sanguinor is evidence of Sanguinius's specific personal continued institutional engagement with the Legion's broader works.