@Sarpedon Well, since nobody else has suggested anything yet, maybe have Vorgen use his (her?) boobs to seduce somebody or other into giving him (her?) a pass into the VIP section of the GBoIA, maybe like an Underhive person handing them out to those who worship "the four most holy aspects of the God-Emperor" (that being a code for the four Chaos Gods, generally requiring a response highlighting the better aspects of each Chaos God, something along the lines of "honour, pleasure, hope, acceptance", but they'll make an exception for the nice lady with the nice tits), and progress to the place from there.
Incidentally, at this point, I'd like to point out to everybody for whom it's relevant that Lucius' path to the VIP section of the GBoIA was specifically long and overcomplicated for a reason, that reason being "having a Chaos gathering place right behind a storefront is frakking stupid as hell". At least two of you did the whole "show the pass, through the doorway, now you're in" routine, and I'd have recommended to whichever heretic planned that layout that they not be such a dumb person. Just saying.