The last, and strongest, of the spirits spoken of in the Book of the Raven is that of the hawk. It was imprisoned far from Skettis, in a shrine on a remote island southeast of Auchindoun.
I believe this description best matches the island we know as Sorrow Wing Point.
The tablet describes the hawk's guardian as nearly invulnerable to the bird's claws. Forsake physical attacks and call down the fury of the stars to defeat this foe. Do not repeat the hawk's mistake.
Now that we have all the essences, Morthis Whisperwing must find a way to combine them into an amulet that you'll be able to use to challenge the raven god, draw him out of the Emerald Dream and defeat him. I'll be sending him my notes on the spirits with the hope that he'll realize the value of my insight.
Each of the spirits has blessed a charm I've prepared for you.