The Sunstone

The Sunstone is part of Battle Preparations in The Witcher 3. Avallac’h’s plan against the Wild Hunt needs an elven artifact called the Sunstone, hidden somewhere on Ard Skellig. Finding it takes Geralt through Skellige politics, a skald, some shady pearl divers and an ancient crypt with Philippa Eilhart.

How to start The Sunstone

The quest starts when the ship arrives in Skellige. It is a level 28 quest worth 500 XP.

Finding Ermion

Ermion (Mousesack) might know where to look, but finding him depends on who rules Skellige:

Cerys or Hjalmar on the throne: Crach sends you to Kaer Muire, where Ermion is arguing with Madman Lugos. Lugos orders an attack, and you have to kill him and about ten of his warriors. Then follow Ermion past Holmstein to talk.
Svanrige on the throne: at Kaer Trolde, Birna is making a deal with Nilfgaard. Svanrige defies his mother and kills the emissary, and you help fight off the Nilfgaardian soldiers.

The skald or the pearl divers

Ermion does not know where the Sunstone is, but points to two leads. The skald Eyvind, watching for a legendary white whale on a cliff west of Arinbjorn, will help, but only if you never mention Ermion. Otherwise, find the pearl divers in an underwater cave on the eastern shore near the road to Eldberg Lighthouse. Either way, the answer is the Ancient Crypt. Back with Yennefer, Philippa offers to go with Geralt, while Yennefer helps Ciri with Child of the Elder Blood.

The Ancient Crypt

Philippa opens the crypt and repairs a broken staircase along the way. Inside wait a siren with drowners, an Igni Place of Power, a venomous arachas guarding chests and a spike trap (use witcher senses, or Aard or Igni to reveal the spikes, then pull the lever), a golem, and Wild Hunt ghosts. A side room by the golem holds the sword Naevde Seidhe.

The mirror puzzle

The Sunstone appears when a single beam of light runs from the central crystal through the mirrors to the platform where Philippa stands. Start with the mirror on the right that reflects several beams, turn it with its lever so the light only goes to the next mirror on the right, then turn each of the other two once. A ghost guards each lever. Philippa then gives you the Sunstone and flies off as an owl.

Tips

Clear your inventory before you go in. The loot, including swords from the ghosts, can easily weigh 70 or more.
Leave through the secret door the puzzle opens, rather than going back. There is more treasure, and you come out north of Rogne.
Lugos usually dies here, but his unique gwent card can still be obtained. See Gwent: Skellige Style.

Walkthrough

If Cerys or Hjalmar rules: ask Crach where Ermion is, go to Kaer Muire, kill Lugos and his men, then talk to Ermion north of Holmstein.
If Svanrige rules: go to Kaer Trolde, help fight the Nilfgaardian soldiers after Svanrige kills the emissary, then talk to Ermion.
Talk to the skald Eyvind west of Arinbjorn without mentioning Ermion, or find the pearl divers in the underwater cave on the eastern shore.
Talk to Yennefer. Philippa joins you.
Travel to the Ancient Crypt (by boat or signpost) and follow Philippa inside.
Kill the siren and drowners. Optional: use the Igni Place of Power, fight the venomous arachas and cross the spike trap to pull the lever.
Kill the golem and take Naevde Seidhe from the side room.
In the Sunstone chamber, turn the mirrors with the levers so a single beam reaches Philippa’s platform, killing the ghost at each lever.
Talk to Philippa and take the Sunstone (500 XP).
Leave through the secret door for more loot.

Quest Consequences & Choices

Who rules Skellige decides how you find Ermion: a fight with Madman Lugos at Kaer Muire, or a battle with Nilfgaardian soldiers at Kaer Trolde. Mentioning Ermion to Eyvind makes him refuse, sending you to the pearl divers instead.