Amulet of Abnormally Awesome Ankheg Summoning

Reveal Hephernaan's dark plan to foil the nature to Ferrusk, who'll cease the deal with the evil creature and give the amulet to help you fight the crusader. You may also kill Ferrusk for it, but be aware the druid is also involved in two other side quests: The Good Druids and Slime Sickness.

In-game description
"Crafted by the dark druid Ferrusk, this amulet resembles the curved pincers of an ankheg hanging from an iron chain. The pincers' polished green carapace catches the light, gleaming with an emerald sheen. Ferrusk created this amulet to summon a passel of ankhegs to fight at its wearer's command."