The Alpha Legion attacks the Sol system in earnest, sowing chaos in preparation for the Warmaster's assault. They trigger riots, anarchy, and civil disturbances across the system, and even manage to infiltrate the Imperial Palace. Rogal Dorn orders the head of his personal guard to assemble a specialized team to hunt down and defeat the Alpha Legion infiltrators, one of whom is revealed to be Alpharius himself. The two sides play cat-and-mouse across the entire system, culminating in the Battle of Pluto. The Fists are able to outguess and outmaneuver the Alpha Legion, and in an unexpected twist, Dorn kills Alpharius in hand-to-hand combat. Omegon's left to pick up the pieces and assume the mantle of his twin, in a bitter jest.
- Angsty Surviving Twin: Omegon has a minor breakdown when he realizes he's alone now, and is forced to assume Alpharius' role as Horus' lackey against his own desire to return to the Imperium's fold.
- Because It Amused Me: This is the reason why Andromeda-17 agrees to work with Archamus and Kestros. The idea of sussing out and thwarting the Alpha Legion’s schemes intrigues her, and she seems to enjoy the hands-on work of interrogating perps.
- Bringing in the Expert: Archamus recruits Andromeda because the Selenar gene-cults helped create the Legiones Astartes and have special insight into their individual natures.
- The Cavalry: Just as it seems that the Alpha Legion is about to win the Battle of Pluto, the Imperial Fists’ fleet comes thundering back into the system, devastating their ships and forcing them to retreat. Dorn himself teleports in to fight Alpharius personally.
- Complexity Addiction: The Alpha Legion's penchant for intricately designed plans with hundreds of moving parts is analyzed and deconstructed here, with Dorn noting that their plans are unnecessarily complicated and frequently counterproductive in the long term even when they succeed. Some of the Legionnaires themselves seem ambivalent about this tendency.Phocron: We can't help ourselves, can we?
- Crazy-Prepared: It is revealed here that the Alpha Legion has had sleeper agents planted on Terra since before the beginning of the Heresy, hypno-indoctrinated with plans for every eventuality.
- Deadpan Snarker: Andromeda drops a few cutting remarks at the expense of the Fists.Andromeda: Your master is barely competent at interacting with anything that does not have a trigger, but at least he has identified that my weakness is curiosity rather than ego.
- Heroic Sacrifice: Even though he's on the verge of death, Archamus lunges at Alpharius just as the Alpha Legion primarch is apparently about to land a killing blow on Dorn in an effort to stop him. Subverted, however, because Dorn saw it coming and turned in just the right way to block the attack.
- IKEA Weaponry: Bordering on a Scaramanga Special; the Pale Spear can be broken down into a bunch of innocuous cylinders and shards, letting eveyone carry it around.
- Killed Off for Real: Alpharius, which came as a major shock to readers.
- The Kirk: Archamus. As the leader of the team assembled to hunt down the Alpha Legion operatives who have infiltrated Sol, he serves as the balance between Kestros and Andromeda, taking advice from both of them while he considers how best to run down and eliminate the Alpha Legion.
- Last of His Kind: Archamus is the last survivor of the Twenty, the first Astartes raised to the VII Legion after Dorn took command. Many of the Imperial Fists, even those who are his equals in rank and seniority, regard him with awe because of this.
- The McCoy: Kestros tends to argue for the bluntest, most direct approach, and gets angrier more easily than does Andromeda. He also debates her on the ethics of her interrogation methods (namely locking someone in an overheated room until they're suffering from dehydration). It's implied that this is why Archamus recruited Kestros specifically; he wanted someone to provide him with this kind of perspective.
- Monumental Damage: An Alpha Legion kill team successfully infiltrates the Imperial Palace and blows up sixteen of the eighteen statues of the primarchs that stand in the Investiary, leaving only two intact: Dorn and Alpharius.
- No Kill like Overkill: Dorn cuts off both of Alpharius' hands, runs him through with his own spear, and then pulps his skull with his chainsword. Then Alpharius' body explodes in a flash of light just in case you needed to be sure he was dead. Although, given this is Alpharius, you probably did need the extra proof.
- Oh, Crap!: Alpharius has a rather spectacular one when Dorn not only shrugs off being Impaled with Extreme Prejudice by the Pale Spear, but starts pulling the weapon in deeper. The most cunning primarch suddenly finds himself with no way out and a supremely pissed Dorn glaring him in the eye.
- Old Retainer: Archamus is a veteran of the VII Legion who has spent decades in service to his primarch.
- Perp Sweating: Quite literally. Andromeda-17 locks a suspected Alpha Legion operative in an overheated cell, waits until he’s almost dehydrated, then offers him water in exchange for information. It works.
- Personality Swap: It's revealed at the climax of the novel that Alpharius swapped his identity with Kel Silonius as part of his plan to infiltrate Terra, leaving Silonius in command of the Legion's fleet while he was smuggled onto the capital planet.
- Riddle for the Ages: What was Alpharius really trying to accomplish? The Alpha Legion attack is apparently meant to soften the system up prior to Horus’ arrival. Alpharius himself claims that he came to give Dorn victory, but never gets to elaborate on what he means by this before his brother kills him. note
- She Knows Too Much: At the end of the novel, Andromeda assumes that this is why Kestros has shown up at her holding cell. He informs her that Dorn has decided otherwise.
- Shut Up, Hannibal!: Alpharius tries to talk Dorn out of fighting him by claiming he’s there to give him victory. Dorn responds with his chainsword.
- The Spock: Andromeda serves as the logical, rational counterbalance to Kestros’ blunt, more emotional point of view.
- Take Up My Sword: A variant. Though Archamus doesn't personally ask him to do it, Kestros takes on his name and his position as a Huscarl after Archamus dies fighting Alpharius.
- Teeth-Clenched Teamwork: Andromeda has no love for the Imperium and makes this clear several times throughout the book. She has good reason to be bitter, since one of her previous incarnations was killed by Space Marines during the Imperium’s conquest of Luna.
- Tragic Keepsake: Archamus was originally named Kye, but renamed himself after a fellow Legion aspirant who was killed in a training exercise because of a mistake he made. After Archamus is killed in battle with Alpharius on Pluto, Kestros takes the name for himself.
- Trigger Phrase: Alpharius took on the identity of one of his Headhunters, Silonius, purposefully wiped his memories, and had himself smuggled into the Sol system. From there he acted as Silonius himself. Each time he met another XX Legion agent, there would be an exchange of passwords that also served as triggers to unlock his memory, just in time to fight Dorn.
- Villainous Breakdown: In the moment after he gets both arms carved off and his chest split open, but before the finishing blow lands, Alpharius is left stammering in disbelief, unable to comprehend that it was Dorn who actually managed to beat him in the end.
- Wham Episode: Dorn kills Alpharius, for real, and Omegon is forced to permanently assume his brother’s identity.
