Crest of Thunder
Cannot be traded.
Thunder courses through the skies, delivering immense power from the heavens. One of the Great Elements, it binds all elements into one.
Feed to your Eidolon in the Eidolon Menu. Permanently increases Eidolon CRIT by 1 - 3. Hold Shift while you click to separate stacks of items.
Various monster drops and treasure chests.