a Deus Ex Machina is an entity or character that appears with no precedence in the story to immediately resolve the plot. Given that Elder Scrolls are prominent in the lore, and their potential is known (But not understood) I don't really think this qualifies.
The Crucible in Mass Effect 3 was a plot device, the catalyst(Starchild) was a Deus Ex Machina.
Still, I'm unsure of how exactly an Elder Scroll is supposed to do something to the sun. Maybe the belief that Coldharbour is simply an example of Nirn's future is true, and using the Elder Scroll hastens the transformation?
Ah - Finally someone articulates the correct definition of a deus ex machine!
This is a fantasy game for pete's sake! Pause a bit and consider that. I have played only one ES game - Skyrim. I've looked up a few things on-line that i wished to get more information about, and most was useful. But I still take this as mindless entertainment - albeit well done.
I have read many fantasy novels in my life, and in the Second Chronicles of Thomas Covenant, their world was under the influence of a magical bane that altered the appearance of the sun, and caused a whole lot of other damaging effects..... So for me mucking about with the sun - I can handle that.
Given my limited exposure, The Elder Scroll idea actually works for me as a focal point of a DLC. Given the plot of vampires attempting to take over the world - now
THERE"S something original - someone trying to conquer the world! (no one has a problem with that as a tired element), i can see how they can write a story involving obtaining an elder scroll to effect their aim of blotting out the sun. (I can simply tell them: all they need to do is storm the College of Winterhold and get it from the library there.) I will of course be getting the DLC, and hope it is worth it.
I hope I haven't offended any purists, but I play for the simple enjoyment, I don't take it too seriously, and so far I've been able to tolerate the story. I guess those of us without enough knowledge of the ES lore are at an advantage here - we can simple ooooh and ahhhh at what gets tossed our way.
I guess I'll hold off getting my Lycanthropy cured!
Can't wait to see how it turns out - I hope it's long enough!