The Harbingers hail from the Feral World of Birmingham, also called the "Black Planet" because it is shrouded in darkness. The Chapter is known to specialise in voidship boarding actions and planetary drop assaults.
During the 13th Black Crusade, led by their resolute Chapter Master Nimrod Grudge, the Harbingers presented a highly mobile force capable of mounting a lightning counterattack against any gains taken by the forces of Chaos.
- Gothic War (139.M41 - 160.M41) - During the Gothic War, in the Gothic Sector, the Harbingers' Battle Barge Unrelenting Fury intercepted the Ork-controlled Space Hulk Scylla and delivered a series of punishing salvos against it. The Unrelenting Fury suffered severe engine damage from repeated Greenskin Attack Craft attacks but was otherwise unharmed.
- Battle of Piscina IV (997.M41) - The Ork Warlord Ghazghkull Mag Uruk Thraka assaulted Piscina IV as a prelude to his return to Armageddon. According to uncorroborated reports, the Harbingers fought alongside the Dark Angels Chapter against the Greenskins. While ultimately defeated, Thraka was able to field-test a number of "tellyporta" devices with which he later intended to bypass Armageddon's formidable defences.
- 13th Black Crusade (985.999.M41) - After the start of Abaddon the Despoiler's 13th Black Crusade, the Harbingers withdrew from battle with the Orks of the Piscian Belt and contributed eight full companies to aid in the defence of the Cadian Gate from the Despoiler's advance.
- Unrelenting Fury (Battle Barge) - The Unrelenting Fury is a Harbingers Battle Barge that was damaged in battle during the Gothic War against the Ork-held Space Hulk Scylla.
- Chapter Master Nimrod Grudge - Nimrod Grudge is the currently-serving Chapter Master of the Harbingers.
The Harbingers primarily wear blue Power Armour, which includes the helm, power pack, torso, groin and shoulder plate trim. The shoulder plates, arms and legs are yellow. The black squad specialty symbol -- Tactical, Assault, Devastator or Veteran -- is located on the right shoulder plate. A yellow Roman numeral is centred on the squad specialty symbol, indicating squad number. The colour of the Aquila or Imperialis on the chest plate indicates company number in accordance to the Codex Astartes -- i.e. White (1st Company), Yellow (2nd Company), Red (3rd Company), etc.
The Harbingers' Chapter badge is a large ebon sword, pointing diagonally to the left and downwards, with a beaming halo surrounding it, centred on a field of yellow.
- Adeptus Astartes: Successor Chapters (Limited Release Booklet), pg. 50
- Codex: Eye of Terror (3rd Edition), pg. 16
- Codex: Space Marines (3rd Edition), pg. 44
- White Dwarf 281 (UK), pg. 46
- Angels of Darkness (Novel) by Gav Thorpe, pg. 80
- Battlefleet Gothic Rulebook, "To Cleanse the Stars"
- Imperial Armour Volume Two - Second Edition - War Machines of the Adeptus Astartes, pg. 23