The Dead Will Speak

The spirit of Gerstmann materializes before you. The Codex Mortalis mentioned that you would need his head, and by the power of this spell you can make material from that which is immaterial. Then you will need to place it upon a nexus of Shyish so that the head will heed the commands of Shyish.

Defeat Klarent Gerstmann and take his head. Then take his head and place it at the nexus of Shyish that surges in his crypt. Then read from the Codex Mortalis to bind the wind of Shyish to Gerstmann's head, and the head to the Purple Wind's will. Then deliver both the head and the codex to Urias who will use the head to break the will of Ostlanders.