This, actually, was inspired by the "To Kill a Lady of Pain" thread:
If you were going to have a group plot to kill the Lady of Pain, how would they do it? What deep dark secrets would they uncover, or think that they'd uncover? How close to success would you allow them to come, and how much doubt would you leave the players with that Her Serenity had had the matter under control the entire time?
Because, really, doesn't every Planescape campaign need at least one plot against the Lady?
The Bladed Queen has tolerated one attempt on her life in very recent memory. But from that we can infer how she reacts to such things:
She ignores them. Or at least seemingly ignores them, while spinning chance and probability so that in the attempt they destroy themselves. Darkwood, admittedly, was an exceptional character so Her Serenity wove an exceptional counter to his schemes, one that would show what trifling with her entails. Should you be planning something even grander than Darkwood did, the Lady will undoubtedly plan an even more ingenious counter, which will still end in your plan being your downfall.
On the other hand, if you're a leatherhead about your plot, the response will be a simple "I don't have time for you", and off to the Mazes you'll go.