Morgiana's Mirror

 is an arcane item added in Total War: Warhammer II Doomsayers Update. It is a legendary item for Fay Enchantress.

It is a hidden legendary item. The quest is triggered when Fay Enchantress reaches rank 12, and requires the player to have 80% Untainted in Carcassonne (province).

It appears as of April 30, 2019 that the item is currently bugged - listed as an arcane item, but technically counts as an enchanted item which means it cannot be equipped at the same time as Chalice of Potions.

Lore
"Through which the Lady's worldly representative peers into the hearts and minds of enemy Wizards, so she might prepare her defence."

Effects

 * Magic resistance +10%
 * Winds of magic cost -15% (Lore of Life)

Source

 * Reddit thread and Loremaster of Sotek Youtube