This quest is not available in game.
Defeat the Guardian of the Hawk and bring the Essence of the Hawk to Arthorn Windsong at the Evergrove.
<Arthorn's voice addresses you.>
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.