The Cave of Dreams is a Skellige side quest that can be obtained after "Contract: The Phantom of Eldberg", and has suggested level 14.

It involves helping Madman Lugos's son, Blueboy Lugos, as he investigates the Cave of Dreams. You can reach the cave via boat.

When you arrive at the location, you will see Blueboy's ship and his crew. Talk to the man and convince him to let you see Blueboy Lugos. Head onto the ship and talk to Blueboy Lugos. Tell him that you his father sent you.

Head into the cave with Blueboy and his crew. As you arrive to a totem, you will need to deal with some Nekker Warriors. After dealing with them, you will eat some herbs, that will cause some visions.

Keep following your map marker, and head deeper into the cave with the crew. The next vision will be dealing with some Clan Tuirsearch Warriors.

After dealing with that vision, keep following the map marker to the next vision. The next vision involves dealing with some Sirens.

The next vision will be for Blueboy Lugos, and you will be up against a vision of Madman Lugos.

After dealing with the Madman Lugos vision, follow the map marker to the next and final vision, which will be directed towards Geralt. It obviously involves the Wild Hunt, and Eredin. After dealing with the final vision, Geralt will collapse. This will complete the quest.