Void Core
Void Cores can be found as a loot from Anlorvaglems in Ter Mur and Unbound Energy Vortex in Shame.
They are used in two Tailoring craftables: Mage's Hood and Mage's Hood of Scholarly Insight. Recipes for these craftables were obtained during the 2019 Halloween Treasures of the Sea event. Otherwise, they are worth 200 Clean Up Britannia (2011) points.