I went back into the Chamber of Fate and reopened the chest. It did open for me and I received a "Gold Bag". It's a one star item, base value 5 gold. It says, "This bag appeared in a magic chest in the Chamber of Fate. The gold inside is perfectly real though."

What the heck is it? What purpose does/will it serve? Can I get rid of it?

 

Or is this just your characters main gold bag and I've had it the whole time and maybe just noticed it? Though it did display it's what I received opening the chest in the Chamber of Fate the second time.

well that chest was left for you by your forefather (your hero from fable 1 ),when you get online and go to the website it tells you to , watch the video and make the choices during the video ,the choices you make decide what will be left for you in that chest by your forefather , i also belive you can watch it 3 times in a row making all 3 end choices and get everything offered by that chest but im guessing there could be small variations , i belive the main things you would want to get are the feign attack book and the chicken suit for the achievements .and you can get a little gold in the bag you asked about but its just gold i dont belive the bag has any meaning, if you happen to have the limited edition code you will also get the halo suit and halo sword ( 22 damage with 3 augments slots ) at the very beginning of the game when you pick your first will power . its a weapon for the first half hour of the game ,

 i always get the free bewitching augment in the guild cave and attach it ,kill thag and then i go to brightwood to get the 3 easy keys and pick up the slash n burn augment attach it and run around collecting everything i can sell, you can go all the way to the bandit coast collecting things to sell before you even walk into bowerstone market , i can usually make it to 14 to 15 thousand dollars worth of sellable stuff if i gather up stuff from brightwood,bandit coast,forsaken forest , bowerstone market ,old town, and the cemetary then selling it all in fairfax, because you make much more profit by selling everything in fairfax , with all the bandits you kill and potions you drink along the way you can usually get up to a 3rd level will power before you even talk to teresa to get all you can make sure you get the first 2 free treasure hunting books in bower lake before you enter the guild cave . book 1 is by brightwood enterence and the second in by the pond , if you have knothole island be sure to buy 3 crunchy chicks in the gypsy camp so you can do the first knothole quest and pick up the wretchers blade to have a 75 damage sword before you even talk to teresa .

                                         have fun

I had done the online stuff and had the Limited Edition code entered before playing the first time. I got everything I was going to get the first time I opened the chest. Then one time I went back the chest was mysteriously closed again, and I opened it to find a Gold Bag. Does anyone else have it at the bottom of their inventory screen?

Yes probably most of us have, I believe it's from the online games or something like that. And it's useless indeed .