In my setting's history a rome analogue has somehow managed to conquer the entirety of a eurasia sized continent. An advanced bronze age society with significant understanding of magic.
As a cooling period looms they seek to prevent it with magic, which backfires, plunging the world into a millenia long ice age caused by a volcanic winter with multiple eruptions, combined with an already cooling temperature. 99% of the population dies or is killed.
Due to large scale eruptions, significant amounts of ash and lava also blanket the world. Increasing fertility for when the ice age ends. But also making certain cities unsustainable or limiting game reserves.
Humanoid societies would likely regress to the neolithic age, albiet with the benefit of many tools still being viable, as well as the ruins still providing shelter. And stories passed down of the old world.
How quickly would society and technology recover after 1000 years of an ice age, would any books or scrolls survive?