This background is based on that from Imperial Armour Volumes 9 and 10, without any additions from my homebrewed fluff. I decided to write up a synopsis of the official Executioner background due to the difficulty and expense in procuring the original sources. Enjoy!
At the outbreak of open hostilities, Lugft Huron of the Astral Claws sent an emissary to the Darkenvault to request that the Executioners fulfill their blood oath and fight alongside the secessionists. The High Executioner at the time, Arkash Hakkon, recognized the dangerous position that this put his Chapter in but chose to honor their millennium old promise. He ordered the Executioners to support the Astral Claws, gave command to the Lord Speaker of the Dead, Thulsa Kane, and went into exile, seeking death beyond the borders of the Imperium. In this way, the guilt of rebelling against the Imperium would be his alone, and no new High Executioner would be chosen until their debt was satisfied.
In 115906.M41, the Executioners vanguard arrived in the Badab system on board the Night Hag. They immediately began to raid military supply convoys in the rear Imperial lines. However, the Executioners did not launch any major offensives until the bulk of the Chapter arrived in 003907.M41. They immediately launched a surprise attack on the Loyalist outpost on the moons of Khymara. The garrison of Howling Griffons was swiftly overwhelmed, and the Executioners destroyed the outpost, including several listening stations and a vital astropathic relay complex. Once their strategic objectives were achieved, the Executioners immediately withdrew, leaving the surviving Howling Griffons to gather their dead.
The Howling Griffons suffered 70% casualties during the battle, including the loss of the Strike Cruiser Augeias and the Chaplain Dreadnought Titus. Titus had rallied the Howling Griffons and anchored their defense, and the surviving Howling Griffons found that the Executioners had honored the fallen hero, surrounding his sarcophagus with the broken weapons of those he had slain and placing one of their own standards in the Dreadnought’s claws.
It was noted by both sides that the Executioners could have pushed their advantage and wiped out the Howling Griffons, removing them from the war. As it was, the Howling Griffons continued to serve honorably in a reduced capacity until they were officially relieved. Lugft Huron was particularly angered by this act of mercy, but restrained himself from reprimanding the Executioners, wary of Thulsa Kane’s dangerous temperament.
Throughout the Badab War, the Executioners refused to place any of their forces under the direct command of the Astral Claws. They fought as allies, never subordinates, and they defined their own objectives and strategy. This continued to anger Lugft Huron, who could not count on the Executioners to support any of his plans. Even so, he could not force the issue or he would risk the substantial support that the Executioners brought to his cause.
The Executioners continued to raid Loyalist targets, though the Novamarines were deployed to intercept them with mixed success. In fact, following the Loyalist victory in the second battle of Sagan in 330908.M41, Secessionist aggression was limited to raids conducted by the fleet based Executioners and Lamenters. Shortly afterwards, the Lamenters were cornered and annihilated by the Minotaurs, leaving the Executioners as the only Secessionists still on the offensive.
The Executioners continued to harry Loyalist patrols and convoys, and accounted for the majority of ships captured or destroyed. By the end of the war, the Executioners had accounted for 43 merchant ships and 11 Loyalist warships. In addition, they continued to destroy Loyalist outposts and listening stations, including raiding Bellerophon’s Fall and Kyro. During this period, the Minotaurs were deployed to counter Executioners in the hopes that these ruthless warriors would be able to defeat the brutal Executioners. Many battles were fought between the two forces, including a bloody tank battle on the airless moon Uzeal in the Crow’s World system. Neither side was able to achieve a decisive victory; the Loyalists believed the Executioners were based somewhere on the edge of the Dene Stellar Drift but were unable to locate them.