I am extremely new the Urban Planescape Project (therefore Clueless) but am not new to appying urban material to Planescape. During an Epic game I sucessfully ran last year, I introduced a few ideas that were fairly out there and probably will not work with the current storylines you have going, but you may find of use in the creative process.
The first concept is greatest kept secret of the Multiverse:
The Lady of Pain is a Super-Overgod who was born BEFORE the creation of the Great Wheel. In spite of all her power, she must maintain an Avatar form in order to run the things from her home office in Sigil. If anyone pays too much attention to her, their own personal reality would begin to unravel and they begin to bleed out(, after all it is extremely difficult to keep such a powerful deific aura under raps.) It also explains why she doesn't speak. Mortal instantly die horribly upon her speaking because her language is so far beyond mortal comprehension and cannot dumb herself down enough to talk to mortals anyway.
Lastly, she doesn't allow followers or worshippers because in the D&D multiverse because:
a) Being so close to her (which anywhere inside the Great Wheel is too close) it distracts her from maintaining the wheel.
b) Having followers actually WEAKENS her power. (My concept of Overgod is that having mortal followers starts to devolve Overgods to being normal gods.)
The back story for Aoskar is a series of lies and propaganda. Aoskar (like many gods before him) was actually an apprentice of the Lady. He shortened his name after he finished his apprenticeship to Ao (as in Ao from Forgotten Realms) and has his memory voluntarily "cleaned" of Sigil and the Lady while remembering the lessions he was taught. Most of the other Overgods where trained by her too, but all evidence of them was removed.
Why Aoskar's temple remained is a mystery to be discovered later.
Third... which is where you come in... despite all that was said before, the Lady does have followers. Beyond the Great Barrier (which we know as Far Realm) is an ENTIRE other Universe that is an Alternate Earth copy at progression level 9+ and has been cultivated by the Lady for over 50,000 years. Her initial reason for being here was to prevent an all-out invasion by the Illithids (as a part of the Chthulu mythos.) Many different sects exist now that are dedicated to her. An average of 80% of the population Universe-wide give her at least lip-service.
As an incredible twist of irony, she considered synonymous with all that good and true here.
She has guarded this secret society from the prying eyes of everyone and made sure that Illsensine and his progeny couldn't even identify this Universe, much less find their way back to it.
A year ago much of this changed, when a group of heroes let by one master of The Art named Geoff Lastari found themselves transported to the burning city of Dis (, original pre-urbanized version.) Just outside the city, the forces of hell were trying to create a working version of Sigil to try and discover a weakness in it's defenses. Apparently they found one. The Lady responded. She opened a Massive Door on the top layer of the Abyss where one of the Tannari Armies was preparing for another engagement in the Blood War. Linking this door through Sigil and opening another just above the mockery of her place of power. It appeared to the Tannari that this was a blessing in disguise and just marched right on through reigning chaos on all in front of series of events. Meanwhile, Geoff found themselves in a bit of a pickle when they were caught trying to leave the city. Lord Dispater dispatched our heroes to handle the problem at the project area. Through a marvelous display of holy magic, one of our troop named Daramil (Male drow cleric of Eilastree) cast Gate Seal on the Door after he beat the Lady's SR (; had him puzzled about that for a while;) and closed her Door (and doomed himself to servitude.)
What an embarassment for The Lady. She has no ego about such things as someone having the skill to close. to the contrary... she was impressed. But it created a larger problem. If the Baatazu figured out that the Tanaari were transported by on of her doors, the may become bolder. It was time to truly punish them on a large scale effort.
D20 Future invaded Hell.
From compact fighters using Fold-Space tech extensively to Atmo Bombers dropping Tech-based Anti-magic bombs with a 10-mile radius each to Massive Dreadnaughts dropping Zero-Point Singularity bombs, Hell was depleted of Devilpower by over half. Tanaari by the hundred thousands were used as shock troops (simply by suddenly finding themselves displaced on one of the layers Hell.) Once the real body of Asmodeus was found at the deepest pit of the 9th layer, surrender was a foregone conclusion.
As soon as the hostilities stopped, every Tanaari was immediately killed, cutting very deep into the Tanaari's overall resources considerably. (So the Lady doesn't cause a power vacuum and end the Blood War she has allowed to rage for eons end prematurely.)
Most of the Lords survived with the possible exception that Mephistophiles may or may not be Dead (Considering he his palace was at the center of both an Anti-magic dead zone and Ground Zero to a ZPS bomb.) Terms of surrender were drawn up by the Lady herself WITHOUT a single loop-hole (a feat only she could do) and signed by all responsible members of command.
The gist of the document was that they were banned from ever attempting to attack the Lady directly or indirectly Forever. They were also banned from ever mentioning what happened here in Hell... Forever.
It will take 100 years for the Forces of Hell and the Abyss to be back up to fighting strength.
The Abyss will recover much more quickly than Hell if allowed to heal. But... the Lady took this into account too.
Later, with the help of her newest apprentice Daramil, she indirectly help negotiate an alliance between Baator and a new form of fast-breeding Horrid Fiendish Formian race (; they have the Fiendish Template from MM and the Horrid Template from Eberron CS and all are Lawful Evil;) while sucessfully keeping her own involvement secret.
Of course, before she sent this fledgling race to its doom, she had a biological inhibitor introduced into the Queen to permenantly slow the birthing process gradually over the next century as they as they start to turn into Baatazu.
Her job has done, her city was safe... but the Multiverse has been changed.
What will the Future hold for the Lower Planes?
Did the Lady get away with her private war unnoticed?
Will the Baatazu survive even with the influx of this new race?
And what will Evil summoners think when they try to summon a Devil and a giant bug that only vaguely resembles a Formian?
Did any of the Lady's advanced weapons fall into the wrong hands?
Did any Taanari escape to tell the tale?
Will Daramil ever get out of servitude?
Hoped you liked the material. My group did.
As I said before, knowing that this would probably alter a good portion of your established storylines, use any or all of this story as you see fit.
At least I hoped you enjoyed it.