Originally, a wooden door was put in place to seal the hollow mountaintop that Weld was built on, but as Eldannen's longing for the outside world grew, he created the golden and silver Doors, as portals to different times.
The golden Door was made when Eldannen longed to see his Fellan friends in the Fell Zone. The golden Door leads to the past. The symbols on the door represented the beasts in the Fell Zone and beyond that.
The silver Door was made when Eldannen wished to see the future results of something e.g. Annoltis being left in authority. The silver Door leads to the future. The future experienced through the silver Door was dependent on actions that had/were occurring in the past/present.