Nethys: the books actually disagree on whether He was mortal, if so whether He was one singular mortal or whether He's rather understood as the end-state of a process many mortals have undergone, and whether He actually counts properly as a god. If He was mortal, He probably became a god through doing a magic ritual which made Him able to see everything in the universe, which simultaneously made Him divine and fragmented Him into trillions of pieces and drove Him mad. Or maybe He broke into trillions of pieces and then some tiny fraction of them ascended. Or maybe He just saw into another plane where He was already a god and let that god possess Him but the process drove him mad. Or maybe, whenever someone seeks omniscience, they are added to Nethys, and that's why He's mad. 

Hard to say, really.

He definitely is attested to have backed the first pharaoh of Osirion in defeating Ulumat, maybe while still mortal (if He was mortal) or maybe while as a god. In one version of the story He ascended from the defeat of Ulumat. He also tried backing the Naga Pharaoh and immediately drove her permanently and irrevocably insane. After she burned all His temples and (in some accounts) all his worshippers He was more hands-off with the visions.

Irori pursued mental and physical perfection. Gods were more perfect than mortals so in the course of becoming more perfect He became a god. 

Erecura stole the secret of divinity from Pharasma, who punished her by sending her to Hell, or maybe Erecura literally was the secret of divinity, which grew a will of its own, or maybe Erecura just realized the secret of divinity in one of Her visions and then could not be separated from it, and took it with her into Hell seeking Hell's protection from Pharasma, or maybe Erecura foresaw that the secret of divinity would be needed in Hell, and took it there, defying Pharasma, or maybe Erecura is Pharasma's aspect of defiance and hubris, now acting independently from the rest of Pharasma somehow, or maybe Erecura is Pharasma's daughter after Atropos, or maybe Erecura is just a devil who made all that stuff up to make Herself more mysterious.

Golarion has theories about reality like fans have theories about fiction.

Let's zoom in on that Irori business.  That monk of Irori said some things suggestive that there is yet another god meddling in Keltham's affairs for some reason.

How'd he do it.  Did he leave a step-by-step guide.  Has anybody else done it.

He was a high-level monk. He did not leave a step-by-step guide. Over time, powerful monks become meaningfully less like mortals, their bodies less able to affect the state of their minds. Maybe if you take that process far enough you become something more like a god. His followers have sought to follow in his footsteps, but none have yet succeeded.

Okay, maybe in Golarion it's like totally normal for somebody to do something and then nobody else can do the thing for the next... this book doesn't even say how long except that it's been at least two thousand years... but in Civilization that's not normal.  Keltham can't help but find it a bit suspicious when combined with the whole Starstone business.

Are there by any chance stories about very advanced Irori monks suddenly vanishing and not showing up in the afterlife?

There are a couple references to some who attain enlightenment and then leave to wander the universe and are never seen again?

Yes, this again reminds him.  Didn't Carissa say something about Aroden searching the universe for thousands of years and not finding anything?  What does the library think is Out There?

There are definitely a lot of worlds out there with people on them. No one knows what Aroden was looking for but it's generally agreed He didn't find it. 

Humans?  Nonhumans?  Do they know how to mine spellsilver cheaply?  Is there any trade going on here?

This library does not answer the question of what Aroden found when he spent thousands of years searching. 

There is not any trade going on here.

That's really bizarre, library.  Even if Interplanetary Teleport is 9th-circle, you'd think there'd be, like, people occasionally taking 100 pounds of spellsilver in one direction and coming back with 100 pounds of diamonds, because they're relatively cheaper or more expensive on planets.

(Keltham has 'figure out what diamonds are' on his menu, but he's expecting it to be complicated and has been previously focusing on spellsilver.)

Osirians think it'd be incredibly cool to trade with other planets, if you could figure out which ones would trade with you. You cannot just go 'a habitable planet around that there star' to target an interplanetary teleport.

But if the aliens - on other planets, or other planes - aren't showing up to Golarion to help, then their planets are all disaster areas of their own.  And if the desolation is that uniform, it's probably maintained by divine mandate in the places prophecy still holds, every plane except this plane, or every planet except Golarion - the scope of prophecy shattering isn't clear.

Or the aliens, if they're more advanced, aren't a kind of thing that cares about the mortals on Golarion.  Or the gods are preventing them from helping...

Anybody seeing a flaw in that reasoning?

....'desolation' seems like a very strong word for Golarion, which is a pretty nice place to live. If everywhere in the multiverse were like Golarion that'd be really good news.

It does seem that the aliens do not have easy interplanetary transport themselves or else don't want to trade with Golarion, or else can't. 

...possibly due to lack of prior literature analyzing the Great Silence, the Osirians do not seem to have grasped the concerning aspect of the reasoning, 'Well, this here planet of Golarion looks possible to fix, though, if we did fix it, the obvious next course of action for Golarion Civilization would be to launch trade and rescue missions to all these other planets and hypothetical other planes, none of whom are already here with trade or rescue missions for some reason.'

Speaking of planet-destroying threats, does the library have any more info about Rovagug.  What It is, where It came from, why people think the world will be destroyed if It gets out of the Dead Vault, that supposed prophecy about Asmodeus letting it out, what international agreements are in place to stop Rovagug cultists like the ones who supposedly went after Keltham, why the cult hasn't been just been stamped out already...

According to the Windsong Testaments, just after the current incarnation of reality came into being, Pharasma took her first step off the Seal in fear of something chewing and gnawing beyond her perception. Her next steps led to the birth of the first deities and one of the new gods stepped forth beyond Pharasma's first fearful step, and in so doing would be transformed and absorbed by that fear. None can remember whether that fear became Rovagug or was Rovagug in the first place In the earliest days of creation, Rovagug was tasked with burrowing through the Abyss.

As mortal life began, Rovagug gnawed his way out of the deepest Abyss and jumped across the Astral Plane to invade the Material Plane. He consumed seven worlds, but as they had no names nor histories, their taste was dull, and he only put up a token fight when the other gods drove him back to the Abyss.

After Asmodeus killed Ihys, Rovagug sneaked into the Material Plane again and fed on the world where the murder took place. As its inhabitants died in agony, Rovagug revelled in the taste, and he proceeded to destroy countless worlds. During this period, he rampaged through Axis in the greatest calamity that ever befell the Eternal City, laying waste to many districts which have never recovered to this day.

Sarenrae decided that Rovagug would have to be defeated, and gathered under her banner an unlikely collection of gods: Abadar, Apsu, Asmodeus, Calistria, Dahak, Desna, Dou-Bral, Erastil, Gozreh, Pharasma, and Torag, along with a number of other gods from more remote parts of the world.

Many gods died in this battle, but their names have been forgotten; certainly the gods who sided with the Rough Beast will never be remembered.  Calistria lured Rovagug to Golarion and distracted him while Torag and Gorum forged the shell of the Dead Vault and Pharasma imbued it with potent wards against escape. Sarenrae then sliced open a rift in the Windswept Wastes on Casmaron on Golarion's surface, sending Rovagug stumbling into the Dead Vault. Dou-Bral impaled him with the Star Towers that prevented him from hearing prayers, and the archdevil Asmodeus bound him with a key crafted by Abadar that only the Prince of Darkness could turn. Sarenrae then repaired the rift, leaving behind a smooth scar and instructed her followers to avoid it. Rovagug's defeat marked the end of the Age of Creation.

According to the Concordance of Rivals, when the End Times come, Rovagug will be freed by a desperate Asmodeus in the hope that he will consume the other apocalypse. Indeed, Rovagug will devour the rest of creation before consuming himself, leaving behind only Groetus to turn off the light of the cosmos and a Survivor to rebuild it anew.

Rovagug's cult is illegal almost everywhere; however, sometimes some people will independently decide that the universe should be destroyed, and will tend to become cultists of Rovagug. No matter how frequently or harshly a society stamps them out, some new ones will tend to show up; to some tiny insane fragment of Golarion's populace, 'the universe should be eaten' is apparently a popular stance.

Also, some countries refuse on principle to make any religions illegal. Sometimes this is used as a pretense for their neighbors to invade but it's not so much more powerful than other excuses to invade that the countries that do it have been wiped out already.

No one knows what exactly would happen if Rovagug were freed. The best case scenario is probably that the gods are able to reimprison him at the cost of merely the destruction of one or two of Golarion's continents and everyone on them. More horrifying scenarios involve Rovagug getting into Axis again, or just succeeding at not being reimprisoned at all and running off to eat lots more worlds.

...Keltham will turn his attention to (real) (on this layer of reality) geopolitics, trying to figure out the landscape of countries who ought to hear his lectures or go in on a counter-Cheliax alliance to actually build Civilization.

And then to magic, browsing books of spells to see if he can spot any obvious ones that Cheliax decided not to tell him about.

Does this library have books of standard commercially available magic items with prices, like a catalog or something?

Yes, absolutely!!

(There are a lot of spells Cheliax decided not to tell him about.)

Amulet of Proof Against Location and Detection, 35,000gp.  Contains a warning that amounts to 'basically does not work for crap against powerful casters'.

Mantle of Spell Resistance, 90,000gp or so if you can find somebody to make you one, special commission.

...it's funny how prices that would've once made Keltham want to run screaming into the night make so much less of a difference, once he's not sure the money is real.  It seems like - computer-game money, now.

Okay.  His brain is full.  Enough library.

Keltham needs to - find out if they located Ione Sala, and were able to get starting info from her, or if he's on the critical path delaying everything.

He needs to find out how much time it takes to learn to cast wizard spells in here, because he feels naked without Prestidigitation.

...he feels like he needs to put the Splendour headband back on, and he's going to ignore that part.

They located Ione Sala. She is willing to sell them what she knows, and he should take as much time to rest and reorient and learn about Osirion as he'd like. Everyone is very concerned about him and the general advice for someone in something resembling his reference class would be to go spend a lot of time at a monastery or something not trying to transform the world.

It doesn't take that long to learn how to cast cantrips in here; they can get him a tutor this afternoon, if he'd like.

Most people in his reference class may not be called upon to wipe out a large circular area of Cheliax at any random time in the next week.

He'll take the tutor, please.  How long does it take to learn to cast from third-circle wizard scrolls in here?

Depends a lot on the person, but if he makes it a priority and has the best tutor they can get him (he does) he should have it down in less than a week.

Osirion strongly expects that the actual worst case scenario here is that they teleport someone in to Cheliax with a peace treaty they wrote up before Keltham arrived, and tell the Queen she can sign in the next five minutes or the country is destroyed, and then she signs. Obviously they can't send that person if the Pharaoh doesn't actually prefer destroying Cheliax to taking other available actions, here, or if Keltham would help with the threat but not the followthrough, but He does, and Keltham would too under the relevant circumstances, and Cheliax will know it. So Cheliax is almost certainly not going to actually get exploded.