You get to loot Boreas' Treasure Room after you have defeated him in Eternal Winter.
- Purchase or pickpocket Forgotten Language Of Faery from Victoria, the orc librarian in Cyseal.
- Head back to the castle and speak to the most northeastern sentry along the wall next to the Earth statue. It looks like the other of generic sentries along the walls.
- The answer is 5 (Lurrean). This disables the force field.
- Your options for the next door depend on which version you have.
- If you have the original version of D:OS, you can deactivate the Sentinels by heading to the East wall before the stairs and pulling a chain on the wall. This option is not available in the Enhanced Edition. Otherwise:
- Since the door is only open when the last pair of sentinels (which are invincible) don't detect any intruders, brute force can't get you through. However, you can use a high level of sneak or invisibility to have one member get past all the traps, and then transport the rest to join.
- Alternatively, sneak or use invisibility to have one member get close enough to the open door to throw a transport pyramid through.
- The left sentinel controls the gate, the right sentinel the lava trap right in front of it. You can use the iron crate to block the sight of the left sentinel, then either use a skill or resistances to pass the lava summoned by the other sentinel.
- If you have Royal Guard Talisman from The Chest by the Well, wear it now and stand in the center of the grate for about 10 seconds to receive the Winter Ring and 5000XP.
- Use Forgotten Language Of Faery to unlock the Chest With Scriptures.