What exactly did Nagash do to the Nehekharan pantheon? A brief skim of his wiki entry tells me nothing about him "carving corpses from the desert gods to be receptacles for the prayers of the dead", as Borek put it.
Nagash's timeline is:
-Born, becomes a priest of the mortuary cult, usurps his younger brother, becomes king
-invents necromancy, begins construction of the black pyramid.
-An alliance of priest kings overthrow Nagash, and exile him for nearly 1000 years.
-Nagash comes back, wages a war against Alcadizaar the Conqueror, and casts a ritual that kills all the living in the kingdom.
-Skaven free the still living Alcadizaar, who uses a warpstone blade to slay Nagash.
-Alcadizaar pulls an Isildur and fails to destroy the Crown of Sorcery. It falls into the hands of Kadon the Mad (not to be confused with Kadon the pokemon trainer), and gradually drifts northwards into the lands that would become the Empire.
-Nagash wakes up as an undead horror, invades the Empire, and gets bullied hard by a barbarian with a shiny hammer.
So Tylos and Kavzar had already fallen when Nagash destroyed Khemri with his ritual of death in ~ -1151 IC. Nagash rose to power in ~ -2000 IC, and as Mopman states above, Tylos probably fell around ~ -1800's.
The only thing that fits the timeline is the creation of the Black Pyramid, which if you read between the lines, is basically just a giant waystone. He did create the first vampires at this time. No word of him doing anything to the gods, however, unless you count him usurping the mortuary cult's divine rituals into necromancy? Instead of mortuary rituals being prayers to the gods, they are now corrupted into "prayers for the dead"?
So it's the invention of necromancy that Borek is referencing, rather than anything direct against the gods themselves. But that still leaves the question of what happened to Khsar?
Hang on, I'm going on a bit of a wiki tangent now.
Nagash had to invade and conquer the other Khmri cities to fund the creation of the Black Pyramid, and I've just noticed that Khsar's patron city was Bhagar. Bhagar was originally home to desert nomads, who were originally conquered by Settra, and were famed for their horses. Nagash practically wiped the city off the map, enslaving most of the city, with "hundreds of refugees" fleeing to spread word of the atrocity.
Could Khsar have been one of those refugees? If so, that gives us a rough founding date for Tylos at around -2000 IC. The Skaven timeline on the wiki put its founding between -2500 and -2000, with a wandering clan of dwarves from the Black Mountains settling there in -1950 IC. "Many advances in architecture and engineering are achieved" in this time period.
Wait—was the Doom of Kavzar orchestrated by a
dwarf? Why did this Black Mountain clan leave the mountains and settle in a human city? They were nomads and wanderers before—and Khsar is a god of
nomads. The fact that they were wanderers suggests that they were one of the factions that rejected the Ancestor Gods, rather than embrace them as the Worlds Edge dwarves did.
So Nagash profanes the rituals of the mortuary cult with Dhar, creating necromancy. He conquers Bhagar, and Khsar, who was once the City Father of Zorn, leads the survivors north to Tylos. Khsar discovers a clan of wandering dwarf exiles, and invites them to settle down, becoming His people. The Dwarves call Him Kazvar, and the humans call him Tyleus, maybe? A century latter man and dwarf begin work on a great temple. A hundred years after that, it's completed, and the Doom of Kavzar occurs.
The Tilean version of the myth claims the Dwaves of Tylos were killed by the Skaven first, but the dwarf version claims that at the very end the last survivors of both races stood side by side.
What if it was a civil war? The dwarves who remained true to Khsar siding with the humans, whilst the dwarves who sided with the "grey hooded stranger" became the Skaven. The Black Mountain clan came seeking their old gods—and they found
two of them.
The Skaven put the founding of Tylos as early as -2500 IC—but Khsar couldn't have arrived there any earlier than -2000 IC. Could the Horned Rat have been there first?
The Tylosian coins are fairly straightforward. They don't have the date of minting like modern coinage, but you're able to deduce a year for all of them by the date they started being deposited. Most of the golden coins are dedicated to either Myrmidia or a man who appears to be the city's legendary father of the Tilean people, Tyleus. There's also representations of Verena, Morr, and Shallya, as well as a God you don't recognize. From the symbology you'd guess Taal, except you're fairly sure Taal is one of the Northern Gods, and wouldn't have been known to the ancestors of Tilea. There's also some of the Dwarven Ancestor Gods scattered throughout. The silver coins are largely dedicated to temporal rulers, and judging by their turnover either they were elected to a temporary position of power, or Tylosian politics were especially rambunctious. You also see several dedicated to local prestige projects, temples and aqueducts and bridges and lighthouses. In some of the chronologically last coins, the depictions of a grand tower sends a shiver down your spine when you realize what it must be depicting.
Hmm, the most important coins are mainly dedicated to Myrmidia and Tyleus, but Verena, Morr, Shallya and the Horned Rat are all also represented. The ancestor gods are included as well—well, there was open trade between Tylos and the Karaz Ankor, so maybe many of the Dwarves still honoured the Ancestor Gods? And it doesn't really prove that Tyleus and Khsar are the same—why would the "Faceless Wind" have His face stamped on a coin? That said, Borek called Khsar "the City Father", so maybe they are the same?
So Tyleus (who might be Khsar, evidence inconclusive) founds the city around -2500 IC. Circa -2000 IC Khsar leads both human refugees and dwarf nomads to the city, who settle down. The Horned Rat is there as well. A great temple to the gods is constructed, but the Horned Rat usurps it. His followers become the Skaven, and kill everyone else. Khsar is broken by this, and becomes the champion of the Beastmen—perhaps some sort of memory of Bhagar's noble herds of horses slain by Nagash lingers on?
