Brittle Spelltome

Source
This item is a potential reward from the following Class Hall missions:


 * Oh So Pretty
 * Ancient Secrets
 * Turtle Soup
 * Singed Feathers
 * Unwelcome Visitors
 * Symphony of Ruin
 * Tip the Scales

It is also a quest reward from normal Broken Isles world quests and can be found inside Curious Wyrmtongue Cache.