For instance, why did the protagonist wish to enter the tower? A modern mind might ask, but this is not a modern story. It is simply to be taken for granted and the adventure that follows shall come.
One of the many reasons I love this chapter is that we begin to see the protagonist take on the identity of a knight, through his brotherhood with the other two figures and through his battle with the giants. Also being the son of a king adds a royalty dimension.
The old lady says that the protagonist will share with them "in present song and in future deeds", so like I was talking about nobleness of mind/deeds in the last chapter, the old lady now confirms that the protagonist will grow into a nobleness of deeds, much like the knight.
Again there is this bittersweetness, that they felt they would be victorious in battle but die in the process, that permeates the entire book. The songs reinforce this theme.