A few misunderstandings above.
First of all, nowhere does it say that you can see Sigil from the Outlands. I like to think you can, since I like the paradox of "you can see the top, but you can also tell it's infinite just by looking at it - it's the idea of infinity itself that you're looking at." This isn't Zeno's paradox, it's true infinity, miles without limit, and yet there's a top! Suck on that, people who think the planes can be understood logically.
But none of that's official. Officially, there's no indication that Sigil's visible from anywhere but inside Sigil. Taking the Planescape books literally, the Spire just goes up and up and disappears in the blueness of the sky.
Secondly, Aoskar's location just prior to his death is unclear. There are some strong hints in some sources that he did indeed dwell physically within Sigil, inside what would become the Shattered Temple. There's a reference to the Lady casting Aoskar out of the Cage into the Astral Plane - whether this is meant literally, or merely means she cast out his faith is unclear. On the other hand, other sources are more reticent, careful to say only that his cult had become very powerful and people in Sigil committed the heresy of worshiping the Lady of Pain as Aoskar's aspect.
This is a fairly crucial point. If Aoskar did not dwell in Sigil, it means the Lady of Pain definitely has the power to affect things outside of the Cage. WE DON'T KNOW THAT THIS IS THE CASE. It's called the Cage for a reason, and one of those reasons may well be that the Lady of Pain is imprisoned there, powerless to affect anything outside the bars of her prison. If he did dwell in Sigil, it means that the Lady didn't always have a ban on powers entering the City of Doors, and that has major ramifications, too. It would mean that all the theories that the Lady of Pain kills those who worship her because if they did, she risks becoming a god and becoming banished herself are definitely false.
For these reasons, it's best things remain ambiguous. Thus far, they are.
First of all, nowhere does it say that you can see Sigil from the Outlands. I like to think you can, since I like the paradox of "you can see the top, but you can also tell it's infinite just by looking at it - it's the idea of infinity itself that you're looking at." This isn't Zeno's paradox, it's true infinity, miles without limit, and yet there's a top! Suck on that, people who think the planes can be understood logically.
But none of that's official. Officially, there's no indication that Sigil's visible from anywhere but inside Sigil. Taking the Planescape books literally, the Spire just goes up and up and disappears in the blueness of the sky.
Secondly, Aoskar's location just prior to his death is unclear. There are some strong hints in some sources that he did indeed dwell physically within Sigil, inside what would become the Shattered Temple. There's a reference to the Lady casting Aoskar out of the Cage into the Astral Plane - whether this is meant literally, or merely means she cast out his faith is unclear. On the other hand, other sources are more reticent, careful to say only that his cult had become very powerful and people in Sigil committed the heresy of worshiping the Lady of Pain as Aoskar's aspect.
This is a fairly crucial point. If Aoskar did not dwell in Sigil, it means the Lady of Pain definitely has the power to affect things outside of the Cage. WE DON'T KNOW THAT THIS IS THE CASE. It's called the Cage for a reason, and one of those reasons may well be that the Lady of Pain is imprisoned there, powerless to affect anything outside the bars of her prison. If he did dwell in Sigil, it means that the Lady didn't always have a ban on powers entering the City of Doors, and that has major ramifications, too. It would mean that all the theories that the Lady of Pain kills those who worship her because if they did, she risks becoming a god and becoming banished herself are definitely false.
For these reasons, it's best things remain ambiguous. Thus far, they are.