Okay, it's earlier than I expected, but it looks like I've got some time to post, so...
Firstly, Tuerny, you rock

. From the elemental plane politics to the stooge factor, I'm stealing a bunch of it. Especially since I saw that you and I had
both used the clock to frame the scenario... only you'd framed the scenario in
time instead of space. And while your setup might have been lacking a bit, you more than made up for it with a crafted scenario that could go a lot of different ways... without ending the scenario. So, I know this isn't
nemmerlesque critique, I just really liked your scenario.
Now, on to my thoughts on mine.
Elements: My use of the rousing music was weak. And I think that the fragility of the clock was not tied well enough into the scenario. Despite these two weaknesses, I thought that my use of the 1/2 fiend xorn, salamander couriers (with the etched metal messages) and betrayal were all very good. I'm pretty mediocre on the throne of fat - it wasn't weak, but I didn't bring out the lovely imagery it screamed for!
Major Flaws: Definitely need to go over it with a fine-toothed comb for knowledge magics. Xiang could perhaps be given some good counters.
For combat, also, Xiang should perhaps have more bite

.
Ur Shannar, on the other hand... Well, we disagree on how scary Ur Shannar is, but for me, it boils down to this: a wizard can potentially (25% chance)
banish Ur Shannar in a single round. Ur Shannar can potentially (~60% chance) kill a CON 12 wizard in a single round. Me, I'd find that scary. (work shown below)
Wizard, INT 20, Banishment, save DC is 22
Ur Shannar, Will save +16, has to roll a 5 or less to fail (25%)
Ur Shannar, BAB 38/33/28, spear dmg 3d8+13 (including specialization) (avg 26.5)
Wizard, AC 20, hp 70, Ur Shannar has to roll a 1 to miss
3 hits = avg 75.5 hp, wizard dead or dying
Stepping On Intent: Agh! Yes. I'm generally good enough (or evil enough) that I can pull this sort of thing off, but a prepackaged scenario for public consumption needs to have everything covered. Not everyone can be a seasong

. Divination protection for certain aspects of the intrigue (so the players have to
work their spells to get the data) would be the big first step for that.
Xiang's CHA 12: Actually, if I'd statted everything out, he would have had higher WIS and CHR for his cleric class - I saw him as being built like a PC, rather than strictly a xorn. But I, ah, didn't actually communicate that

.