Sorry, that was slightly mis-phrased. What I meant to ask/say. Was that I abandoned 1 save, as it wasn't possible to defeat the boss. Using another save, in which, I hadn't picked up the shards. Running straight to the boss while still having stat boosts. In which case, I defeated it and was removed from the dream.
To confirm. In my newest save, I didn't pick up the shards before exiting the dream. So, my question was. Is that particular area, inaccessible from now on. Therefore, the shards and whatever else may be there. Forever gone? OR. Is it that area eventually comes back?
The boss itself isn't exactly easy. But with the boosted stats, it is quite possible. You unfortunately lose those if you run around too much. So that's why I used another save and went straight to the boss.