Sigrun knows of Thorog and will lead the way to examine the dragon's corpse.
'You seek the dragon Thorog? Ah ha ha ha ha! You are a bit late, my friend. The undead worm was soundly defeated by a group of adventurers. If you wish to see where they won their glory and Thorog fell, I will show you.
'And you have come from the Lonely Mountain, have you not? In return for this favour, you will answer the many questions I have of the dwarves who dwell there, as we go.'