I've sort of avoided purchasing dark glyps so far in the campaign, as I really have no clue how to work it out. In Vanilla Descent, unless I'm mistaken, you take the number of glyps you need for the quest (including the Dark Glyps among them), put one normal glyph in play as the players' starting location, then shuffle the rest, meaning that the Dark Glyph will appear at a random point in the quest.
How does it work in RtL? Obviously you would not get one Dark Glyph per level (that would be VERY silly), and since some levels have one face-down glyph, and others have two, you don't exactly know how many glyps to shuffle your Dark One with.
Then again, there's no mention of Dark Glyps anywhere in the RtL rulebook, so I was wondering if they were even allowed. Have people used them? If so, how do they use them?