You learn that The Jailer is seeking The Primus's sigil in Chapter 4 - The Last Sigil, and find out that The Primus hid his sigil in the vaults of Korthia shortly before he disappeared. You also learn that The Jailer wants the five sigils of the Eternal Ones to unlock something called the Sepulcher of the First Ones. Of course, you need to try get to the Sigil of the Primus first - which you manage to do, but you find it's all tangled up with the magic of a memory - similar to those memories you've been bringing to the Runecarver. You bring the Sigil of the Primus to the Runecarver to see if he can help untangle it, and it has an incredible effect on him, turning him into The Primus. Unfortunately, The Jailer and Anduin attack and are able to take the Sigil of the Primus from you, but you do manage to escape with The Primus to Korthia. You make plans for the Covenants to forge new sigils, and resolve to defend The Arbiter's sigil at all costs.