This is the Kabal I've been working on, on and off since 2002 or so. Some slight changes have been made since the new codex came out, but the fluff as a whole is mostly unchanged.
Kabal of the Tacit Tongue
Archon: Quall D’Ren (uses Lady Malys rules)
Dracons: the nameless
Haemonculi coven: The Silence
It is widely accepted that The Silence manipulated events to put D’Ren in his position as Archon. Some say The Silence constructed D’Ren from the souls of fallen Wraithkind Dracons. Some even believe that The Silence somehow acquired a piece of, the fallen Eldar God, Lileath’s heart, and where able to partially reconstruct it. They believe this heart beats within Quall, and that is the reasoning behind the Kabal of the Tacit Tongue’s sudden and violent rise to power over the last few millenia. This, of course, is all conjecture and lacks proof because even under the harshest torture the Tacit Tongue could not speak a word even if they wanted to.
What is known is that the Tacit Tongue was once part of the Wraithkind, and consequently instrumental in it’s failure to usurp Vect. They still maintain the Wraithkind’s color scheme of Neon Blue and Black on their armour, but have added bright reds and crimson to their uniform, replacing the yellow. During the Kabal’s inception, a ritual was created in which all initiates surgically have their mouths removed by The Silence. These Haemonculi created a way to liquefy trapped soul energy and all Kabalites feed intravenously (most of the time infused with some sort of combat/recreational drug). In becoming a member of this Kabal the initiates throw their existence to the whim of the Haemonculi. If any member where to dissent they would starve. It is this that keeps D’Ren safely in his position as Archon without much fear of constant assassination attempts from within.
It has been recorded that Quall meditates before battles and has determined outcomes with extreme detailed accuracy. Long ago Quall fought two Eldar farseers for several hours. When it seemed as though the battle was a draw D’Ren soul-trapped the farseers. These souls where given to The Silence, who fashioned them into a fantastic set of blades. The Seerblades have become a thing to be feared on the battlefield and stories are told about how they destroy entire squads in a swirl of neon death. Unfortunately, sometimes the Farseer’s souls synch with each other in a way that the blades become difficult for D’Ren to control, but the benefits to the working blades heavily outweigh this drawback.
The Kabalites of the Tacit Tongue have studied thousands of written languages as a means of instilling fear in alien races by using their own languages as a form of psychological warfare. Many hive cities and craft worlds are targeted repeatedly by the Tacit Tongue. During a raid, the only sound from the Kabal's Raiders is the hail of Splinter fire and the screams of the slaves taken. The Kabalites graffiti is left to warn of future raids. Sometimes the graffiti is in paint. Most of the time it is in the blood or entrails of their prey.
Asdrubael Vect has left the Tacit Tongue to their own devices mainly because the Kabal was so essential in felling the Wraithkind and Quall D’Ren has never been a threat to his throne. That doesn’t mean from time to time he won’t pit the Tacit Tongue against a rival Kabal simply to test their strength or D’Ren’s psychic prowess. Needless to say the Kabal of the Tacit Tongue maintain a certain amount of Vect’s attention.
See also: Cult of Lechery