After all the rave reviews that Demon's Souls got, and the fact that it was developed by From Software, a company whose games I usually really enjoy, I knew I had to have it. So I picked it up and started playing. And I started dying. And dying, and dying, and dying, and dying some more. Good freaking lord. This game may be the second most difficult game I've ever played, the first being Trauma Center for DS. That one will never be topped. Except maybe by I Wanna Be the Guy. Call me any number of noob insults that you want but I personally don't enjoy getting my ass handed to my by any game unless I really, really enjoy the gameplay(Dead Space 2 is a good example). Demon's Souls isn't a bad game by just about any measure. I think it just requires a certain mind set that I just don't have.
Anyway, as for the song, it's from the game's intro and I think it's simply titled Demon's Souls. It's a truly intimidating piece that sets a fantastic tone for the game.
Here it is, courtesy of YouTube user IvanIMG: