Gladhir has told you of a massive grodbog queen high in the cliffs of Cirith Ungol. You will need allies, but defeating her will surely curb the flow of gredbyg in the area.
'${PLAYER}, we recently discovered the location of a massive grodbog queen high in the cliffs. I described her to Legolas; he grimaced and said the name \qMaeganc\q. Perhaps he has encountered her before? The Elves can be quite... cryptic.
'Regardless, I believe she is the source of the gredbyg closest to the camp, and therefore a threat to us. If you are able, I would ask that you and your companions find her and eliminate her before she finds us and does the same! While you are there, please look for a tunnel that may have allowed her passage from Torech Ungol. I do not expect the gredbyg would have travelled such a distance overland; they must have burrowed through the rocks beneath! If you find this tunnel, collapse it, or more gredbyg will come through.'
The grodbog queen Maeganc can be found somewhere in the cliffs of Cirith Ungol.
You should defeat Maeganc and collapse the nearby tunnel to Torech Ungol.
Gladhir came be found in Echad Taerdim, the Ranger camp in Cirith Ungol.
You should talk to Gladhir.