Technically the Vex and Oryx want to escape the heat death via entropy in the universe. We know now the universe won't close, but will keep expanding forever, until all energy is uniformly distributed and no work can be done.

That's up in the air. For a long time we've actually believed the end state we were headed for was Big Rip - the accelerating expansion of the universe would reach a critical threshold and tear everything apart.

I think that consensus has been questioned lately but I haven't followed the research.

The current best guess is this:

In several billion years, the universe will collapse into it's lowest (or lower) energy state since we are most likely in a false vacuum. Studies on the Higgs suggest this very strongly. This would destroy everything in the universe at the speed of light making life impossible. After that, either the big rip or the big freeze as what remains continues to expand, grow apart, and go cold.

As for the big rip, it's not so much tearing everything apart as it is space eventually expanding faster than the speed of light at microscopic scales, making subatomic interactions impossible.

Why? I don't remember the Exo Stranger or any of the Ishtar scientists being mentioned near Osiris, which could be his connection with a Warmind. Am I forgetting something?

In the Osiris Grimoire card someone claims to have proof that he was a Golden Age experiment mis-incarnated as a human. The reasons I think the Exo works for Osiris are because:

1. They both have an obsession with the Vex and are working outside of the City's influence to accomplish their goals.
2. The Exo stranger has a pulse rifle that looks identical to the Fate of All Fools, which was originally the reward for going 9-0 in Trials (in data mining).

Not that this proves anything, but I even asked a Bungie employee if the Stranger did work for Osiris and they told me that was a great question, but wasn't drunk enough to answer it :)

P.S. This doesn't discount the Maya/Stranger theory, could be a further piece of the puzzle. I think if both the Strange and Osiris are obsessed with the Vex they would probably be linked in some way.

And in the timelines where strange and terrible things happened? Unfortunately, I'm not a Marathon expert. :(

The failed timelines are all simply the result of the Nova going off, ripping apart the ships and such. No mention of the wrencancerwhatever. Basically, the pfhor have a weapon to make a star go nova early, and they are using it to destroy Lh'owon. This a problem because everybody will die, and it is though that it will unleash the beasts trapped in the sun.

You end up containing the Nova with technology from the Jjaro space station, saving yourself. All the other timelines have the Nova going off killing everybody.

Is there a good/easy way to experience the Marathon story besides playing it? I've tried, and it was marginally okay, but the oldness of it is a huge barrier to entry for me, I just can't get absorbed in it like I would have experiencing it while new. ):

Can I read all the terminals somewhere? What's needed to understand the Marathon story? Am I losing out on something fundamental by not actually playing it? Etc, etc.

Yes, you need to play it through. Just reading the terminals is no substitute. You can read all of the terminals the marathon story page.

You can also read them (slightly different format) in the Marathon Spoiler Guide:

http://marathon.bungie.org/spoiler/

EDIT: Crap, no you can't. :( But there's a bunch of other info in there.

Yes, you need to play it through. Just reading the terminals is no substitute. You can read all of the terminals on the marathon story page.

Thanks for the link at any rate. I'm not sure playing it is really in the cards, both because of limited time, and because of it's age. Someday I may give it another shot, but that won't be any time soon.