"Defeat the Lurker" is an objective in the main/side/misc quest "The Fate of the Skaal" in Elder Scrolls V: Skyrim - Dragonborn.
Walkthrough
When the structure around the Wind Stone shatters, then it is time for you to face the Lurker. They are difficult opponents if faced in groups. Charge in if you are melee oriented and use Power Attacks. Mages and Archers should fall back and engage carefully.
Defeating the Lurker will save the Skaal around the stone, liberating their minds.
