|Battle Cry||Unknown. Possibly homicidal screaming or yelling "HONOUR" over and over again.|
|Successors of||Imperial Fists|
|Chapter Master||High Executioner Arkash Hakkon|
|Homeworld||Twin worlds of Stygia-Aquilon|
|Strength||Fewer than 1,000 Marines and declining.|
|Specialty||Close-combat and Head-Hunting|
|Colours||Blue-Grey with Red|
"You may cleave to your courage but that will fail you, look to your weapons but you will find them not enough. Run, fight, hide, pray, cry out or cower -- it does not matter, for we are coming."
- Fafnir Rann, first High Executioner
"The man who passes the sentence should swing the sword."
- Eddard Stark. Hand of the King, Warden of the North, Lord of Winterfell.
The Executioners are a Chapter of Space Marines created way back in the ancient days of 1st edition, and then remade by Forge World for their take on the Badab War in Imperial Armor 9 and 10. They are a successor chapter to the Imperial Fists, but if one were to look closer they probably wouldn't be able to see many similarities. Think the World Eaters if they stuck far more closely to the "honourable" side of Khorne paired with the sheer stubbornness and grit of the Iron Warriors.
They're notable for being one of the four secessionist chapters that fought alongside the Astral Claws during the Badab War. Their motives were not heretical, instead they were fulfilling a debt to the Astral Claws who saved their asses a couple millennia before. Whether this falls into the category of Lawful Stupid is up to interpretation, but point is being that they turned against the Imperium solely based around honour and brotherhood.
Most of their beliefs and combat doctrine derives from the Feral Worlds they recruited from, resulting in a high emphasis on honour, dignity, and of course glorious close combat. Of course this can result in a lot of infighting and conflict within the chapter, where it can easily turn into bloodshed unlike say the Space Wolves. Because of this the Executioners also have an unusually high amount of Chaplains in order to keep the Marines in line and to encourage them on the battlefield. They also have a preference for taking the heads of their enemies as trophies, obviously earning them the distrust of the Inquisition.
As mentioned before, the Executioners fought alongside the Astral Claws during the Badab War. However, they always refused to work directly under Lugft Huron, instead working in separate battlefields by themselves and even sparing survivors if their objectives were met. Of course, this pissed the Tyrant off to no end, especially when they turned on the Astral Claws when they had a disagreement over what to do about a surrendered force of Loyalist Space Marines.
During war nearly an entire company was wiped out to the man by the Carcharodons, who did the same to the Space Sharks. It is only known because a Loyalist naval patrol found the battlefield strewn with both Executioner and Carcharodon bodies, all in various states of dismemberment. No survivors were found amongst the bodies and both sides refuse to say anything about it. But with all things considered, the Executioners are technically the only chapter to win a battle against the Space Sharks. Keep in mind, this is the same chapter who waged practical genocide on Badab Prime and who basically trashed Abaddon's 7th Black Crusade.
After the secessionists surrendered, the Executioners were put on trial by the Loyalists alongside the other traitors. After some probing by the Inquisition and being vouched for by the Salamanders, who fought in the war against them, they were deemed redeemable by the court. They were sent on a century long penitent crusade and were not allowed to recruit any new neophytes. In the opening years they were actually pretty damn successful, taking down a pocket empire within the galactic core that was supported by three separate Traitor Legions and another Titan Legion. Even after that, they took down a fucking heretical Rogue Trader Dynasty. Currently they're killing Necrons in and around the Orpheaus sector.
With the coming of 8th Edition, updated rules for Thulsa Kane, and most chapters being reinforced by Primaris Marines, there may be hope for the Executioners. Though considering they're balls deep in Necrons and still haven't had a fluff mention even after the Indomitus Crusade, we won't know for sure.
Last edition's Forge World chapter tactics for the Executioners allows them to ignore any negative Leadership modifier of any kind. (including from lost combats?) Also, all characters, for Sergeants to Captains, gain Instant Death on to-wound rolls of six, but they must issue and accept challenges. If it wasn't obvious before, Executioners are a melee-based army where even Scouts could potentially keep a unit locked into assault and a basic Sergeant with a Power Sword could knock down special snowflakes.
Their special character comes in the form of Thulsa Kane, a Chaplain with a 2+/4++ save, Plasma Pistol, and a S6 Power Axe. Along with Zealot he has Eternal Warrior and allows any friendly model (a single model) within 12" of him to reroll to-wound rolls of one the turn they charge. Bit situational, but can prove useful sometimes, especially if said model is a Dreadnought. His set Warlord trait allows all friendly units to add +1 to assault results and sweeping advance whenever Kane is in a challenge (if he's not, you're doing it wrong). And remember, Instant Death on to-wound rolls of six applies to Kane as well.
No FW chapters have unique tactics yet. As Imperial Fist descendants, they should probably take that tactic, although Black Templars may suit them better. Kane does have an update, however, and is one of the few characters from Badab to come out better in 8th. He is still an impressive beatstick while buffing nearby units with his various auras, and has increased damage in melee if the target is a character.