This quest is given by Gnarus who can be found in the Lykeios but only after the main Teeth of Naros quest is completed. He offers you money to thin out the Pteryx by destroying their eggs. General egg locations can be found below. Once you've found as many as you like, return to Gnarus for a gold reward.
If you go into the sewers you'll find a number of these eggs near the undersewer entrance. These can be repeatedly destroyed in the following way:
- Destroy the eggs
- Do the following two times: go into the undersewers and then back up to the sewers.
- Go back and destroy the eggs again.
- Repeat as often as needed.
Many eggs can be found in the Pteryx Eryies on the eastern part in the Teeth of Naros. There is also a cave near the entrance to the Eryies that has a few. As mentioned above, the sewers also have eggs.
Gnarus can be found in the Lykeios, though he didn't have the gold ring indicator to show where he was even with the quest activated. As far as I can tell, this is a repeatable quest like Myrrine's Marauder Totem quest since the eggs respawn.
Reward was 2,912 gold at level 25.
Conversely there is a quest (The Strange Man) that is in the sewers but never shows up in the Quest logs. Search Strange Man here for details.