I've reached the place that's a large meadow with a creek running down the middle and three glass houses. When you complete all three glass houses, the volcano erupts.

Off to one side, there's a little cave. Inside the cave is a torchlit room with a doll on a table. You can pull the doll with you out of the cave. Would anyone care to share a hint as to what this is for and/or where to take it?