The Eye of Divinity

Source
This item can be found inside the Cache of the Firelord.

The Eye of Divinity as an ingredient
This item is used to make:

Easter Egg
Equiping this trinket in the World's End Tavern in Shattrath City will allow priests to see Ricole Nichie standing next to Haris Pilton.

It is likely the priestess mentioned in the flavor text is Eris Havenfire, whose spirit battles the undead in Stratholme and is involved in the quest to make.