^ Okay, so let me get this strait, for some clarity, you think the "shadowy figure" is thanos and the "enemy even odin and asgard cannot withstand" is surtur? So you think they are talking about two villains here? that is correct? Interesting, while I do not agree with you, I think they are talking about one villain, I can totally see what you said, being what the meant though.
Here is a few things to ponder though, I am not necessarily disagreeing with you Sam, because I can totally see them going with what you think it reads, but here ARE two things I think we should keep our minds open about.
"Predating the universe itself", okay, well one, is that to be taken on literally? It sure is, I would say so. Now, since you said the beyonder and galactus and TOAA are the only ones who predate the universe, wouldn't it be possible for them to change Surtur's history a bit as well, if they would change Thanos'? See what I am saying? Since you said they may make Thanos older than what he is in the comics, they could do the same for surtur as well. And Surtur has been around since the dawn of the universe, so if the whole "predating universe" enemy has a changed history, it could be Thanos, OR Surtur.
The only thing that is making me hesitant about that, is remember Starlin signed off for Thanos in Guardians, and avengers 2, if Thanos is going to be in this movie, why wouldn't he have signed off on him for this as well? Ya know? I think this synopsis can be read as a few different things, tthe whole "shadowy enemy" thing could be taken literally, or metaphorically, I mean, in a synopsis, I wouldn't be surprised if it was supposed to be metaphorically. But it could really be either.
I just feel Kurse, Malekith, Backround Surtur, and Backround Thanos would be a bit too much, and as for that, I think they are talking about one enemy here, given how I view the synopsis almost as like, well a small paragraph, if you will, the last sentence to me seems to be summing up the few details of the rest of the synopsis, a conclusion if you will. Which which I am leaning towards surtur personally. Though I could see it being both, plot wise. I just don't know how it can be thanos if starlin signed off on him for gotg and avengers 2, why wouldnt he sign off on this?
And I really hope this movie stays exclusively to Thor's world.