You access the pedestal again; the platinum discs suddenly appear once more in your backpack. With the knowledge of the stone watcher learned and the discs returned to your possession, the time has come to return to Thunder Bluff and inform the Nara Wildmane of your discovery.
Welcome back <name>. Were you able to use the discs to your advantage, or was it for naught?
You were missing some discs? Interestingly enough, it seems that the discs of Norgannon are only parts of the complete set - like keys on a key ring, if you will. If we can find the Plates of Uldum, then we could actually access the Uldum complex itself. I don't know whether to be excited by that prospect, or be terrified. We may need to risk everything to ensure that those secrets the earth keeps which would destroy us all remain just that - secrets.