I'd like a DLC questline that involves the psijic order and the great collapse.
The mages of Winterhold summon you to the college because they have found a way to get more information on the great collapse. The want you to go to a dweller ruin containing an ancient alchemy lab with the ingredients to make a potion that can have the drinker go in a dream state and relive events of the past of the place where you drink it.
After finding the lab and making the potion you have to bring it to the college and drink it there. You enter the dream state and are taken back to the final days before te great collapse. When you exit the college via the bridge you enter into the flourishing city of Winterhold where you have to investigate.
You learn that the destruction of Vivec and the resulting eruption of red mountain have nothing to do with the collapse, but that rogue elements within the Psijic order are involved. The dream state ends when the city of Winterhold sinks into the sea of ghosts, killing nearly everyone including yourself.
Back in present Winterhold you inform the mages of your findings. They contact the psijic order to confront them. The psijic order informs them that a long time ago, some members left the order and went rogue. They tell the mages where they think their headquarters is and you are sent there. In the underground headquarters you fight your way to a chamber containing texts from the time of the great collapse that explain that the rogues used old dwemer technology to build a weapon that causes tremors by generating shockwaves that can destroy entire landmasses. The college of Winterhold was spared only because the mages of that time were able to dissipate the wave before it reached the college. Their magic caused a feedback wave that destroyed the weapon. They were however not aware a weapon had generated the wave.
There is also a journal in the room that tells the members of this order have found the necessary parts to recreate the weapon and are planning to use it in the near future on the college to destroy it. The journal has a map that indicates the location of where the weapon is built. You have to go there and destroy the weapon.