About ninety thousand years ago, late in the Golden Age of Man, a school of Vyanoweir cartographers tore a seam in time and never closed it again. They had set out to do the opposite. The reconstructed grammar of Deoric was more fluent in Vyanoweir mouths then than it has ever been in mortal mouths since, and a collective among them set their fluency to the leylines. They meant to chart the places where the Elemental Planes press closest to the world, fix those places in inscription, and bind them. What they wanted most was time. An Izzus seam is where the time-layer of the Elemental Planes runs shallow against the material world, and a people who could map every such seam, and re-route the strongest, would hold an advantage no rival could match. The advantage runs through where time-pressure gathers: a stretched moment to close a contract before a rival has read the same report, or to mend a wound faster than the body can answer. They wanted to own the map of it.
The work asked two masteries at once, and that is what made it rare and what made it heresy. Inscribing into a seam needs Deoric at the grammar level, the composed command that can state a thing's nature and hold it to that statement. Finding the seam in the first place needs Kethic attunement to Izzus, the trained feeling that tells a shaper where the time-layer surfaces. Almost no one has ever carried both. The seam-scribes, as the few surviving references name the collective, did. They went down to the place the maps now call Estornum Agnostus, opened the seam with feeling, and began to write into it with command. The inscription took. For a while the seam answered the grammar laid into it. Then it came apart under the writing, and what tore did not mend. It was the first such tear anyone kept account of, and not the last. Tens of thousands of years later the Tolarian mage-kings drove the planar anchors of their Apparatus of Severance into the same Izzus seam beneath Elderran and tore it again on a far greater scale, stranding a whole capital out of step with the world where the seam-scribes had stranded a single stretch of plain.
This was nothing like the disasters that bracket it in the histories. The World Fire was a plane spilling across the world; the Oblivion Years, a great age later, were a slow void-collapse that hollowed out the people who lived through them. Nothing at Estornum Agnostus burned, and nothing emptied. What came loose was the seam's own substance, the hold that time keeps on a place, and it bled into the ground and stayed there. The flat grasslands above the western coast have run wrong ever since. A traveler who crosses them loses the order of his own days while he stands on them.
The curse the Plains carry
The way the wound takes a person is specific, and that specificity is the clearest proof of what it was. Memory sits at different depths in time. What a person has held longest is rooted deepest; what happened an hour ago has the shallowest root of all. Where the torn seam bleeds, the shallow roots will not hold, and memory fails from the top down. The last hour goes first, then the season behind it, then the years behind that, the loss working backward through a life. Someone who lingers keeps the trade he learned as a boy long after he has forgotten why he walked onto the plain, keeps a childhood song after he has lost the name of the companion who walked in at his side. The oldest memories are the last to go, and often they never do. This is the curse the Plains of Oblivion are known for, and the curse is older than anything else about them. The palace of forgetting that a grieving half-titan queen later raised over the same ground is a far younger layer, built on a disorder ninety thousand years old before she ever came to it.
The floor of Estornum Agnostus, where the seam-scribes worked. A disc of titan-bone set into the rock, broad as a threshing yard, cut all over with a Deoric that no living reader can parse and that flakes away a little more each time someone tries. The lines do not meet where they ought to. A surveyor's eye follows them and insists the disc is wider across than around, and measures it twice to be certain, and gets two answers. The Jae-Kai who come each year to mourn here do not measure it. They sit at its edge until they begin to forget why they came, and then they go, which is how they know the visit is over.
Nobody at Estornum Agnostus understood what had been done, and the people best placed to explain it were the first the disaster took. The seam-scribes died at Estornum Agnostus with the working still held in living memory, and the record of how they had composed it was lost with the rest of the Vyanoweir corpus when the libraries burned, fifteen thousand years later at the close of the age. What is known now is a modern reading, argued backward from the wound by shapers who can recognize a torn Izzus seam for what it is. The Golden Age itself left no account of the cause, because the one place the cause was written is the place that takes the record back. Later fire-cultures gave the act its name. The Neferati, and the Tarkhetan tradition descended from them, keep a long fear of the one working a shaper must never attempt, the inscription of a living seam; when they name that heresy, this is the catastrophe behind the name. The warning that came down from it is shorter than the disaster that earned it. A seam is read, never written.