Asmodai
Repent, Motherfucker! - Asmodai
Asmodai is the Master of Repentance of the Dark Angels. He is the oldest and most experienced of the Interrogator-Chaplains, and also the most obsessed with hunting down the Fallen Angels and making them repent. SHOWING HIS INTENSE BURNING LOYALTY TO THE GOD EMPEROR.
He is NOT the Grand Master of Chapter's Chaplains however; that position belongs to Sapphon, though he's not as famous as Asmodai. NOR is Asmodai the greatest of his craft, that honour belongs to Molochia who made ten heretics repent instead of Asmodai's paltry two. So Asmodai is pretty much only known for being one of the angriest fuckers within his Chapter, his rage fuelled by his self loathing at only being almost the best at everything.
Biography
Starting as a no-name tactical marine in the eighth company (that's what the book says, but the 8th company are Assault marines) Asmodai was a fairly unremarkable soldier. It was only when he was the lone-survivor of his first encounter with one of the Fallen Angels when his career actually took off: as there was no-one else to explain the situation to, Asmodai was taught the secrets of the chapter and was offered a position in the Ravenwing or the Deathwing. He chose neither and declared he would be a Chaplain instead as his obsession with finding the Fallen and exacting revenge started taking root.
He captured his first Fallen in 411.M41, but failed to make him repent when the Fallen died without confessing, which meant right off the bat he sucked at his job. This obviously caused Asmodai to enter deeper levels of RAGE and then started going to unhealthy lengths to capture more to slake his angry streak. With renewed vigour, Asmodai caught three more Fallen over the next 25 years, but still managed to kill each of them before they could repent. Normal people would have taken this as a sign that their chosen profession was not for them, but Asmodai was no normal man. So the Inner Circle decided to give him one they'd caught earlier before Asmodai exploded with pent-up frustrations. Asmodai broke this one in one single eighteen day session of physical and mental torture. When Asmodai emerged from that cell smoking a cigarette, he had earned his first black pearl and he smiled for the first time.
His obsession has grown and bled into the other aspects of his life as a Space Marine, and he's basically become the "fun police" of the 41st millennium. When Asmodai bombarded an Imperial city to flush out a single Fallen, Azrael had his command privileges revoked and transferred him to the 10th company so he could learn humility. However, when a bunch of recruits didn't answer his questions as enthusiastically as he liked, he ordered them all killed because he thought their gene-seed might be contaminated by "tardiness". When he heard someone from the Seventh Company laughing while inside the Rock, he had the entire Company sworn to silence except for hymns and communicating in battle. He doesn't actually have the authority to do any of those things, though. At least, not without Azrael's approval (which he won't get), he just tends to threaten the officer in charge when he doesn't get his way. Besides, a vow of silence covers speech. Laughing is not speaking.
Unfortunately this zeal to track down Fallen has led his chapter into some big troubles, like where he countermanded a Captain's orders and diverted a Dark Angels strike force from their position fighting Orks to investigate rumours of a "remarkable warrior". It turned out that warrior was in fact an Inquisitor of the Ordos Xenos, and that the Dark Angels unauthorised repositioning had cost the allied Silver Skulls most of their army. Not only that, but the Inquisitor returned to the Silver Skulls homeworld to explain exactly what happened and demand assistance in punishing the Dark Angels for their behaviour. Wisely (and partly for fear of going head-to-head with the Unforgiven) the Silver Skulls Chapter Master instead requested that Azrael come and explain himself personally. So Azrael had to set aside his duties for a time to go and apologise for what happened. During that time Asmodai was grounded under lock and key until the Supreme Grand Master got home to decide what to do with him. When Azrael returned to the Rock and asked if Asmodai was sorry yet, Asmodai responded that he was sorry he didn't kill the Inquisitor when he had the chance.
At some point, Asmodai was passed up for promotion to High Chaplain, despite his seniority in age and the respect/fear he has earned within his Chapter. The position instead went to the much younger and more conservative Sapphon (who is secretly not conservative at all and is tasked with the curse of being the Chapter's most radical, unorthodox member). Asmodai openly states this was a bad idea, since he sees Sapphon as weak and indulgent. In comparison, Sapphon (and most of the other Inner Circle Masters, and probably just about everyone else) sees Asmodai as psychologically unstable and a destabilizing influence on others.
Azrael has had to rein him in or cover up for some of his more excessive actions, but he keeps Asmodai around because, say what you will about his sense of humour (or lack of it), he delivers -- if there's a Fallen Angel (or even someone who might know something about a Fallen Angel) out there, he will track it down. Interesting that despite his long service and obsession he has only able to make TWO fallen repent and apparently killed many more by accident, implying that he's really just a sadist asshole. His preferred tool of interrogation is a torture weapon called "the Blades of Reason".
Quite ironically, Asmodai is named after a daemon king of lust in Christian mythology. So while WH40K Asmodai is busy fun-policing the galaxy, daemon Asmodai is conversely busy living it up, Slaaneshi-style.
Asmodai is the chapters rabid attack dog, but he is loyal to a fault and will never bear his fangs against those within the chapter that are of higher rank. His zeal and commitment can be infectious to those that follow him into battle and the inner circle are very weary that he may end up pushing the lower ranks in a Less then desirable direction which is why the level headed Sapphon was given the top job instead; as they know that if Asmodai was ever to gain a position of higher rank then it could only mean trouble for the chapter.
The inner circle are very much aware that Asmodai is a mad man straining at the leash but his zealous hatred is always pointed towards the enemies of the Imperium, so they simply need to point in the general direction of the enemy and shout “Asmodai I can see one over there” and then smile in satisfaction as the enemy promptly empty their collective bowls as Asmodai turns his violent attention their way.
Asmodai himself is very much aware that he is mad, during “The legacy of Caliban trilogy” a city sized Daemon tried to get inside his head and attempted to corrupt him. Asmodai’s inner thoughts can be summed up as “Am I Mad?... WHO FUCKING CARES, TIME TO KILL ME SOME TRAITORS” and using the power of “Rage” banishes the Daemon from his mind and then charges into an army of poor Daemons and butchers everything that he can get his hands on.
Tabletop
Asmodai made a semi-welcome return to the tabletops in the 6th Edition codex with new rules and a new model. Sadly the DA's 7th Edition codex didn't make him any more useful, or viable. His page is actually right across from the generic Interrogator Chaplain, making it very easy to see how useless he is in comparison.
He is a WS6 interrogator chaplain with no upgrades, except for his trademark "Blades of Reason", which is a no-frills close combat weapon with the Instant Death rule... he also scores +D3 victory points if he slays the enemy warlord in a challenge. Which despite his WS boost and instant death capability, he will likely find difficult to achieve.
Being an Interrogator Chaplain he causes Fear (they all do that now) which doesn't help him so much, since his WS is high enough that he hits most of those things susceptible to Fear on 3+ anyway and dropping those things from 4+ odds to 5+ odds when they hit back is not something to be jumping for joy over. Neither is an instant death weapon that has no bonuses to-wound nor any AP value; if you get REALLY lucky you might insta-gib a monstrous creature by rolling a 6 to-wound and it failing its save, but you're still probably better with the more reliable Crozius against those anyway, while you were always insta-gibbing humans/tau/eldar with that crozius to begin with...
Unfortunately, you are probably much better served taking a tooled up nameless Interrogator Chaplain in your force instead of Asmodai, which is a shame since his fluff is so hilarious. However, this makes perfect sense as taking someone good at their job is often better than taking someone who is zealously terrible at it.
8th edition
He got leaked early, and first impressions are... looking a little better, but not enough to fix the fundamental problem with him: you're probably better off taking a normal Interrogator-Chaplain. His Blades of Reason are still S-user AP-nil, but under the new Damage characteristics they deal D6 damage compared to his Crozius's damage of 2, and with most models in the game having more wounds this might be a risk worth taking. He's still an Interrogator Chaplain statwise (that is, under their new statblock, so he has 5 wounds and an impressive WS 2+) so he has "all Dark Angels within 6 inches re-roll failed to-hit in melee" and "all enemies within 6 inches have -1 Ld", plus his own personal ""all Dark Angels within 6 inches have +1 attack". The problem is, he's expensive, 145 points (or Power Rating 8) to a normal Interrogator's 90 (Power Rating 7) and doesn't have the option to buy a power fist.
2nd Opinion: Take him, a Deathwing Ancient with TH+SS, and as many deathwing knights as you can deep strike. There's nothing in the rules or indexes stating +1A buffs do not stack, so Asmodai and the ancient (while powerful choices in their own right) turn deathwing knights into something that would make slaanesh blush. hitting 4 times (sergeant 5 times) on 3's rerolling failed hits, S8, -2 AP (-3 for Sergeant) 3 damage each (2 for Sergeant but the wounds carry to different models). Charge these avatars of rape into TEQ and watch your opponent cry.