I just thought this might be an interesting thing to tack on.
Optional Ending: The Great Planar Shattering
While the 'canon' events of 3E Planescape assumes that the players successfully thwart the evil plot of Dexter to destroy Law and Order in Multiverse, enterprising Dungeon Masters may use this event to segue their way from 3E Planescape into the upcoming 4E of Dungeons and Dragons. In this case, the brief awakening of Aoskar in the heart of Sigil is enough to transform the whole of the Multiverse.
The Illuminated Eye's resurrection of Aoskar briefly touches upon fundamental forces that the Planes are built upon. These are the same forces that allow belief to shape the Planes, the power of the Words that Orcus used to slay his fellow gods, and what positions Sigil at the heart of the Multiverse. It is a one in a trillion event that briefly allows Aoskar to awaken his wrath against a cosmos that spurned him.
Countless new portals are opened up in Sigil as thousands more are rendered inoperative while Aoskar's energy flows through them. The infinite nature of some domains is ended while many become nothing more than floating islands in the Astral Sea. The Abyss' unlimited source of chaotic energy is suddenly cut off as that realm is forcibly transformed into a convergence of the Inner Planes. A massive sea of elemental chaos replaces the once separate and divided Elemental planes.
Asmodeus, never one to miss an opportunity, takes this moment to finally seize the opportunity he's long awaited and become a full fledged power. With most of the gods having already had their realms torn from the Nine Hells, this is the perfect opportunity and he becomes undisputed master of Baator.
These two events, occurring side by side, more or less result in an unthinkable happening; the Blood War finally ends. There's no formal treaty between the two sides and both fully intend to eventually get back to eradicating the other but all organized conflict between the two types of fiends is officially ended. This is just before the Yugoloths make several binding exclusive pacts with the Ta'anari that are quite lucrative and allow them a large position of prominence in their newly relocated home. Likewise, Malcanthet the Succubus makes the surprising betrayal of Chaos by having herself and all of her minions remade into Devils.
Much of the Multiverse is left rather shell-shocked by these events as no one can really wrap their minds around the majority of them. The Mind's Eye manages to slink off in the distance as most individuals attribute the cataclysmic occurrence to something other than a few well-meaning cutters playing god maker. Nevertheless, after about a week, enough new portals are charted so that business starts returning to normal. The loss of the Blood War is largely replaced by Devils and Demons recruiting nearly equal amounts of soldiers for other conflicts.
If you think the Mind's Eye learns anything from the disaster then, unfortunately, you would be wrong. Those few Signers who are involved in the event are only left with an even more exaggerated sense of their own importance while the Believers involved are convinced that the power to become a god is within their grasp. Depending on whether Aola becomes a god or not, the new Aoskar finds himself with a massive new number of followers who depend on him to help navigate through the changing face of the planes.
As for the Lady of Pain? Sigil is unaffected but for a minor repositioning while the gods walk as softly as ever around her.