My party has traveled to stormreach searching for an artifact and to secure the overlord that might be in/under stormreach ( the overall plot of my story here is that the lords of dust are making there final preparations to unleash the overlords from their various prisons and bring back the age of deamons, and the party is working with the silver flame church to secure these locations and build up their forces for the final confrontation in a few short years.) The artifact is taken care of but I need some help with the actually location and finding of the overlord himself. I know they are somewhere under stormreach influencing the many civilizations that are built apon it to crumble. I need some help thinking of ways my party could discover the ruins underground and what exactly it is that is sealing the overlord.