Thórhall believes that the scent-glands you gathered may lure the hive-queen into revealing herself, allowing her to be slain.
'What do you know, ${PLAYER}; I have had an idea! If you crush the scent-glands you gathered, an overwhelming scent will be released, and the gredbyg will rise up.
'The scent will undoubtedly draw the hive-queen from her hidden nest. If you can slay her, the entire hive will be greatly weakened... at least until they can raise a new queen. That should keep them out of our way for quite a while, and that is the best we can hope for.'
The grodbog-lair is in the Palace of Náin, north of Lamâb-dûm.
Thórhall asked you to take the scent-glands to the grodbog-hive and crush them. The resulting scent should draw forth the hive-queen.
Thórhall is at the small dwarf-camp in Lamab-dûm, south of the Palace of Náin.
You should report back to Thórhall with news of your success.