The Deep Elves were indeed a superpower in the grand scheme of Tamriel's many kingdoms.

But one day they vanished, inadvertently taking the Chimer with them... And the Falmer... and paving the way for the Altmer to take control.

Most experts agree that the Dwarves must have been transported by the god Lorkhan to a separate plane in Aetherius. Some may even remain in Oblivion. But what happens to the other races when the Dwemer return? Will they be on a mission, like the Crusades? Or perhaps they have escaped imprisonment to conquer their kingdom once again. Or maybe they never wanted to leave at all. 

The purpose of this thread is to discuss the many outcomes of the Dwemer's return, assuming they might return someday. If you have information rendering this discussion obsolete, please keep it to yourself. I realize that this may never be possible.

Let's get this party rolling. 

A portal from Aetherius opens in the cavernous depths of Blackreach, ancient kingdom of the Dwemer. The pale denizens known as the Falmer collect curiously around it, unable to see it but still keen to investigate. As they skulk closer a new, powerful presence leaps from the vortex, brandishing a sparking war axe. More follow, slaughtering the Falmer until the Harbingers have purged their home of the filth. A new age of warfare has begun.

The slaves that had long grown out of control. The Falmer would put up a fierce resistance, wouldn't they?

Besides, ignore the intro if you will, create your own scenario. The more creative the better. We can discuss Dwarven conquest here.

The Falmer would have to be eradicated. In the absence of their Dwemer masters, the Falmer have become too aggressive, too independent, and it's not likely they would fall back into subservience. However, the races of men are easily controled. Even the Falmer manage ways to make them their thralls. Plus, many would see the return of the Dwemer as a sign of their true godship, and willingly worship and follow them. 

But it's their numbers, heightened senses and ability to hide exceptionally well that could provide a lasting problem.

Either way, the Dwemer... For what reason could they or would they return to Tamriel?

Liis, you seem to be one for Steady State Theory. Volzah Zol, you seem to be leaning towards the Big Bang.

I, for the prupose of the argument, will remain as neutral as I can... So, let's assume for now that the Dwarves have returned in Blackreach in full force, have slaughtered the majority of the Falmer, and will enslsave the rest. What are their options now? Keep in mind that the rest of the world is still probably unawares.

An Oblivian portal opened and released them from their imprisonment within the realm. They then appeared in their underground dwellings, killing all within, and reactivating their machines.

They then spend time underground, rebuilding, fortifying, enchanting, and defending their homes.

The Dwemer in Markarth (Forgive me if that is the wrong city) then take over the major city, killing all in their way, enslaving the rest.

Feel free to continue the story, because I'm drawing a blank after that.

Den da dwagonbawn awived to kiwl deir ashes...

Face palm.

We get the gist of how this started, do we not? I want to know what you all think about how the other races would react. The Dunmer in particular. Maybe Azura offers the Dunmer a chance to return to their previous form? I think that there would be serious repurcussions from the other nations at the ancient Dwemer's return.

I think Nords would react the most, leading most of the land of course. Especially if they were to get into Markarth, the other Jarls would definitely react. And for anyone who has done the war, Ulfric would react, or the emperor would react (Unless you finished the Dark Brotherhood quest line). They would probably be in a state of disbelief at first, but as the signs become more obvious, they would probably either A: Attempt to negotiate, or B: Simply start a war (Especially if you helped Ulfric in the war). 

When we introduce the dragons of Skyrim, how do you think the Dwemer will react to the Dragonborn literally destroying everything, and who has also explored Dwemer ruins?

Probably kneel down and start praising the dragonborn.