To find this Monster Contract, travel to the Isles of Skellige, then the island of Spikeroog. When you arrive, head to Svorlag village and check the Notice Board. You may also accidentally stumble upon this quest by finding the Ekhidna cave.
The Contract, Nils Disappearance, mentions a groomsman by that name who apparently vanished without a trace. His brother, Kevan, wants someone to go in search of his sibling, so begin by paying him a visit near the fishing hut. His sister bore witness to a monster carrying Nils away, while others in the village think he simply escaped to avoid his soon-to-be wife. Whatever the reason, negotiate Geralt’s reward and go on the hunt!
Head north and explore the shoreline, then climb up the grass-covered hill that overlooks Svorlag. Look around a bit and you’ll see Britt, Nils’ fiancé. Speak to her and she mentions a cave. Perhaps the monster lives there.
Wander south past the Old Watchtower to the shore. Walk up to the cave entrance and kill the Sirens nearby, then head inside. When you enter, slaughter a bunch of Drowners, then explore the chamber filled with water. In here you’ll see a large altar built as a homage to the god Melusine.
Activate Geralt’s Witcher Senses to discover…
- There are scales on this altar.
- Large Siren tracks.
- These scales are a different color compared to ones from other Sirens.
Now take the southeast tunnel, climb the ledges on the right and jump to locate a chest. Go back to the tunnel and go around the corner until you see a fissure. Geralt seems to think a cult came down here to praise Melusine.
You’ll eventually see explosive barrels, so blow them up from a safe distance using Igni Sign magic. Kill the Drowners that appear and follow the tracks south until you see some cliffs outside. Crouch and then inspect the body to discover it is indeed Nils. Whatever carried him off dropped the man.
All of a sudden Melusine appears! Rely on Aard Sign magic, Igni Sign magic, Hybrid Oil and Grapeshot Bombs during this fight.
Destroy Melusine’s health bar and pick up the Lock of Lamia Hair, Ekhidna Mutagen and Ekhidna Trophy. Now go back to Kevan and let him know his brother’s fate. He asks you to tell Britt what happened and you can accept or decline. If you agree, she’s happy you believed her, then offers a reward of her own.