OK, after a year and half pause I am considering running 40k campaign again on same principles as last. Harlock's Legacy + adapted Warpstorm fro Rogue Trader were big success due good character selection, lot of good background material (DoDG), fine story that made gang consider fine Puritanism vs Radicalism differences (with Sister, even Famulae, and even if with Denounced and Condemned trait it was not an easy discussion).

So going after old maxim that people are judged by company they keep and who they call enemies I searched for good Bid (Misterious, mad, bad and dangerous to know if you get it ) and inquisitorial factions they will work for. And voila - Purge the Unclean offers almost perfect BigBad in form of mysterious leader of Serrated Query. Nice. Now, let's find some more background...

Hm, bummer, there is none? Or am I missing something?

Anything more on Adranti, Serrated Query or their master (Yes, I know all that I need to know about 1000 Sons, I need what is he doing ATM)?

Anyway characters, some still in concept phase. Needless to say they serve very radical master...

Female, Noble born, Adept, Cursed Blood of Malfi, Scholar of Colleges Getaireia Lexis

Xenos obsessed daughter of minor Malfian noble. During school days she was secretly purposely fed forbidden texts by Inquisitor as both chance to see how good she is and as blackmail oportunity. Motivation - Power and tradition

Female, Famulae Upbringing, Verispex Adept.

Luck played it's hand with this one, she first rolled 10 corruption (and 10 Fel) on Famulae upbringing table then rolled minor mutation/psyker on divination table... Great things come from random and hence she ended in Inquisition as very good at field of her work and easily blackmailed character. Motivation - nothing mayor so far, player is new to 40k in general so it will take few sessions to see how she reacts to some of more questionable things in 40k. Generally motivation should be attempt to prove her psyker gift is not a curse and is more useful then just her mind, but it never works easy with 1st time DH players.

Male, Noble Born, Guardsmen, Penal Legion.

Scintilan noble family. He screwed his brilliant (and well payed for) military career by refusing to charge some pointless hill and was disowned by family and kicked to penal legion. Motivation - Regaining honor, revenge, tradition.

Male, Scum, rest not yet decided.

From Tranch, tried to join mutant uprising at first but his whole gang was killed by mutans at the moment they met them. As a result, a bit mad he hates mutans more then he hates Imperium. He led guerilla warfare against mutants and was even declared a minor here by Imperial authorities. Inquisitor knows whole story. Motivation - revenge, survival.

Male, Schola Progenium, Arbitrator, Justice Not Law.

Did sanctioned killing on behalf of his precinct captain, but when his captain was purged as too radical (after killing few too highly placed nobles) he had to run. Motive - Justice Think Bud White from "L.A. Confidential"

Female Noble born Assassin or Scum - Character 1 bodyguard/lover.

Psyker, probably one from Dusk, preferably Diviner with Living Nightmare background.

Maybe some periodic characters who would play from time to time - Tech Priest with some interesting background.

Idea for adventures...

So I need that card from Illumination and they played it in previous campaign. I don't want to just give them to them, so introductory adventure will be something based on "The Final Circle of Paradise" . Pleasure world, mysterious deaths, old friend behaving badly, potentially lethal tech artifact (VR goggles using Adranti tech that make imaginaty world appear more real then the real one). What is there not to like?

Purge the Unclean - but I would substitute Shades for something less combat heavy and more roll-play intensive. Other two stay basically same (maybe less "deus ex machina" ending to Baron...

Then one based on "The Invincible" . Backworld planet, missing inquisitorial expedition, Necrons (or are they Necrons? ), nothing to do but to admit defeat. Again, what is there not likable for 40k?

Eloholth...hmm...we don't know for definite what he's up to, but I wouldn't say Thousand Sons.

Note that he was a tutor to Magnus, which means older, which means wouldn't have survived astartes implants (especially something as god-awful unstable as Thousand Sons gene-seed).

So post-human gene therapy, like Kor Phaeron or Luthor, but not astartes.

If you want a "what he did next", though, it's anyone's guess. He's not around in the books, so he went off to do.. things.

The Query are facilitators and fixers but aren't explicitely chaos (though they work with chaos powers if it's profitable). If I was really clutching at straws, I might point at his nickname and the fact that the other 'silversmith' in the Horus Heresy books was responsible for casting up legion lodge medals.

So going after old maxim that people are judged by company they keep and who they call enemies I searched for good Bid (Misterious, mad, bad and dangerous to know if you get it ) and inquisitorial factions they will work for. And voila - Purge the Unclean offers almost perfect BigBad in form of mysterious leader of Serrated Query. Nice. Now, let's find some more background...

Hm, bummer, there is none? Or am I missing something?

Anything more on Adranti, Serrated Query or their master (Yes, I know all that I need to know about 1000 Sons, I need what is he doing ATM)?

You have some in the Radical's Handbook.

Plus, in Disciples of the Dark Gods, you have the unknown heretic, a NPC that could be the head of the Serrated Query.