After completing "Lure of the Abyss", you will be approached by Ser Duncan, bringing message from the Duke. The Duke is impressed by how you slayed the Hydra, and invites you to join the Wyrm Hunt.
He gives you the following writ which confers the status of hunter upon you:
Wyrm Hunt License
IMPORTANT: Make sure NOT to sell the Wyrm Hunting License. You need this permit to access several quests from Ser Maximilian. If you have accidentally sold the Wyrm Hunt License or otherwise lost it, you can try buying a new one from Black Cat, or from Madeleine.
Speak with Ser Maximilian, Captain of the Hunt, near Gran Soren Castle, just outside the castle gates.
Ser Maximilian: It would be my honor to show you the ready charges for the Wyrm Hunt. The choice is yours:
Decipher a text
Aid a research team
Hear the Duke's Directive
Nothing for now
Choose: Decipher a text
Ser Maximilian: As I was setting about to find work for you, I came upon this slate. I know not its origin, nor its age, but the writing it bears is old. So old, our men could only read a few words. "Dragon", "Scar", "Arisen", "Heart". What little we know, all points to you, ser... Your task is to find out if there is anything important written there.
This begins the quest:
The Cypher
Inquire Around Town
Objective
Wyrm Hunt Quest
Investigate a slate bearing a forgotten script. It may reveal aught of the dragon
Details
Seek those in the city who might shed light on the slate's queer script.
Set the quest as active, then open the map and locate the red marker. Go to the fields to the west, just north of the Pawn's Guild and talk to a farmer named Josias. He suggests you ask a Scrivener, or a conterfeiter.
You now need to visit the forger, Mountebank, owner of the Black Cat, on the southeast side of town. He reveals that the slate isn't really script, but rather a Cipher.
Your objective now is to seek further leads.
Locate Maurin. He is moving about town, so use your map to find him. Try the market, shops, or fountain square if you are having difficulties finding him. He mentions a drawing, a figure of Hillfigure Knoll. The man drawn upon the hill north of the Capital.
You now need to travel to Hillfigure Knoll. To get there, travel a fair bit north from Gran Soren, past the river. Watch the cinematic, then speak to the Dragonforged.
Then, go back to Gran Soren and report your findings to Ser Maximlian to complete the quest, The Cypher
