So what happens over the course of one year:
A: The end of the world. The Audric empire has collapsed. All crops everywhere failed under the onslaught of ash. Close to half the populace is lost and presumed perished. Save St. Marrionlee, Eisenfaust and a few other imperial bastions with enough magic to manipulate the weather to keep the ash cloud clear, the rest of the continent lives in perpetual gloom.
B: Those who survive in this world now are governed by just two items: Cauldrons of Plenty and horns of plenty, magic items once used to feed the poor are now all that keep settlements in the ashfall going that aren't city sized like St. Marrionlee that can conjure food using sorcery.
C: Caira has become a Thriae Queen and reached her full size, and per the agreement with Lucia, has built a 20' (and growing) hive in St. Marrionlee, so now thriae are becoming a common sight in the city. The thriae are building their own magic items to weather the coming age
D: The Green has perished, effectively ,or gone into hibernation until the eruption ends. Qulana will no longer gain succor from any covenants with the Green. On the other hand, the Primal side is doing fine now.
E: The Highfather is now one of the most feared terrorists on the continent, having sided with the Iron Duke, his druidic arts and great rituals are slowly converting the residents there into an elemental army of immortals who can survive and thrive in the new age. He has resurrected the primal side druids as a Lawful Neutral organization to appease the Duke. The Greenfield druids have mourned the passing of the age and are now making plans to weather the world in remote places likely to survive.
F: The Siniseid empire decided not to invade and is now starting to be affected by the ash cloud as well. It's less developed and strongly magical, so thus far it's been able to weather weave the eruption away.
G: The Nephilim in the Oubliette is running the place... sort of. It's definitely a horror show there, and nightmares and monsters from the island are attacking shipping.

H: Whatever your PCs get up to in a year. Recruit an army, start a settlement, become a legend for good or ill, fight the good fight, bed lots of lovers, love lots of bedding, discover the true meaning of christmas, have a family, you name it.