"Vyra Ketyra Morsu Ckhay Neuka," Divayth Fyr chanted.
"No," screamed a mage jumping trying to break his conversation.
It was too late. The mages fighting in the war were dead, all of them, and Tamriel was reshaped.
The Nine has left prayers unanswered, and the people are losing faith. The daedra have reopened portals to Tamriel, now that the spell has broken the barriers.
Basically, you are a survivor in this magic-torn world and must either help this place, let it die on its own, or help destroy it in search of power from Dagon.
Cyrodiil
Cyrodiil, the place where the Mage Wars started. It was where Fyr cast his spell and it was hit the hardest. The dead walk this place, daedra roam freely. The forests of Cyrodiil have turned to a blackened, scorched, land. The only safe area in the entire province is the Imperial City. Only Ocato and his most trusted guards are there.
Morrowind
Morrowind, House Telvanni's home. It has been nearly destroyed. In the mainland it is all blackened wasteland. In Vvardenfell its main island has become swamplike. No living man is brave enough to enter Vvardenfell, not only for the giant dreugh that live, but for the crazed survivors. The diseases of Vvardenfell have ravaged the land. Those enter shouldn't expect to come back, alive anyway.
Skyrim
Skyrim, the nordic lands. The mountains still live, as does the snow, but the nords are all dead, but they still walk, as they are the undead. The freezing cold of Skyrim can kill you, if the dead nords don't. There is rumored to be a portal to the Imperial City somewhere in the mountains, should they make it.
High Rock
High Rock, the desert. Daggerfall City has become a place for thieves, rogues, and scum. Various outposts dot the map, some are friendly, others are hostile. It is said there is a dragon in Daggerfall City in disguise. Those who survive in the bandit-infested province will probably stay alive almost anywhere.
Hammerfell
Hammerfell, ever since the spell it has been lost.
Black Marsh
Black Marsh, the Argonian Swamps. Ever since the spell, the disease place has become more dark and dangerous than before. Argonians fight a civil war, slaughtering each other in their madness. When argonians don't kill you, then the diseases do. If you survive the Black Marsh, you are either a mage or have a very-hardy immune system.
Elsweyer
Elswyer, the Khajiiti Desert. The spell turned it into a glass danger. Under the weak glass is lava. The khajiiti show no love for outsiders, believing all of them helped turn their wonderful desert to this glass horror. Any non-khajiit entering Elsweyer can expect being enslaved or executed.
Valenwood
Valenwood, the Bosmeri Forest. The spell of the mage turned the animals into horrible creatures. Walking on their hind legs attacking with their three arms each with seven claws. The beasts of Valenwood are dangerous, the Bosmer hide seeking a hero. One that can cure their lands and bring back their faith in the Nine.
Summerset Isles
All contact with the Summerset Isles was lost after the spell.