"The only thing necessary [...] is for good men to do nothing."
-- Edmund Burke Abridged
You cannot, as a mortal, structure how you'll splinter, on ascending to godhood. If you could, new gods would not be so utterly vulnerable and helpless; things as weak as a newborn god are not generally all that weak. But to be splintered, when you were previously mortal, is to lose all the patterns that directed your mind towards your aims, to be made up of terror and eagerness and loneliness and grief and thwarted plans, all separately, with no guarantee each element will remember that it's meant to coalesce.
Having prepared in advance, having been very wise, having made of yourself something more coherent and more careful than a mortal generally is, helps; but not enough that you could ascend under fire and expect not to die.
Carissa is shaped, all through, for this, and still half the fragments of herself will have hardly any recollection of what they are, or where, or why.
But they know that they might die, if they don't pull themselves together quickly. That's not a truth she memorized for just this one occasion.
And there is not a single fragment of Carissa Sevar which would accept that it might die.
Her pieces begin to pull together, partially, piece by piece, and as they do, She begins to claim Her portfolio and define Herself as a god. Lawful Evil is in that; and also, freed from Zon-Kuthon's grasp, loss and pain, but the surviving of it; from long-lost Amaznen, artifice, knowledge, magic; and even from Cayden Cailean, traces of competition and resolve -
—but there's a problem, now, which is that Pilar Pineda may be stronger than Cayden and not already exhausted, but She is really really not at all experienced at being a god or fighting godwars, and Carissa Sevar is getting larger and more distributed than Pilar can protect just by standing all the way around Her—
And through all the taverns of the world and the wild words that drunks dream up, as is His domain, a rumor was spread—
—though also there were other rumors, contradictory or less alarming ones or naming earlier or later times, to make their way to high officials and those charged with officious panic. But once a time was set and communicated to His representative, then to His true flock and all the ordinary people of Golarion beyond Absalom, to them this tavern-rumor was spread—
That Carissa Sevar
(—have you heard the word about her, that she freed Wanshou from the great elder kraken that ruled it since Aroden's death, and gave it better government; that Cheliax's Queen suddenly bent knee to Carissa Sevar as her Empress, and Carissa Sevar at once began to rein in Cheliax's worst excesses—)
would ascend to godhood on that day,
under the star of Lawful Evil,
and other Evil gods would try to slay her,
for that if she won,
she would rein in Hell,
and create an alternative to horror,
not a paradise, still a place where real evil would be judged,
but where souls would not be shattered for their sins;
and even those already in Hell, whom you fear lost there,
from suicide, from exposing a child they couldn't save,
would then be rescued and given succor—
And of course it isn't believed.
Who would believe it?
It's not the sort of thing that anyone repeats because they believe it.
Godwars don't occur on schedule. Prophecy is shattered, and much of the point of prophecy in the first place was to avoid godwars.
Some people have heard about Carissa Sevar's supposed compact with Asmodeus, and even if you believe that, the compact definitely doesn't say anything about Carissa Sevar being able to save souls already in Hell.
There's no way that Asmodeus would ever allow it. And there's no way that an ascended mortal could ever take Asmodeus. Iomedae isn't that powerful, Irori isn't that powerful—
Irori had always meant to accomplish such feats with the aid of His students, after inspiring others to also ascend.
There's even a ridiculous version of the rumor that has Carissa Sevar somehow doing something about Abaddon and the Abyss! No respectably cynical person would ever let themselves be seen believing it for a second!
There's souls less lost than that, who frequent His taverns; the respectables can be left to their cynicism.