Does anyone have a good idea of how many warbands operate in the vortex? How about warbands of note?

Depending on how you define a warband, from hundreds to thousands of them. Truly (in)famous ones, probably a few scores.

You have few importand warbands in description of screaming vortex.

The core rulebook suggests a few, beyond that I suspect the answer is "however many you want". Sorry, I know that's a tad unhelpful, but unless we see Fantasy Flight Games' release schedule for Black Crusade over the next year or so, we really don't know if rival warbands are ever going to be discussed in any detail.

I would like to see a BC product along the lines of the Renegade Crowns (WFRP 2e) - something that allows random (or selected) building of warbands and their holdings within the Screaming Vortex (or elsewhere).

HappyDaze said:

Renegade Crowns was made of pure win, and a book like that would certainly be great for BC. I'm fully behind this.

Morangias said:

Thirded. Very good call!