Who was Rumpelstiltskin?
I mean, obviously he had magical capabilities. And he had a plan. But what was he going to do with the miller's daughter's/king's baby? Take him back into the earth? And what would this accomplish?

So many of the other fairy tales seem obvious in their symbology but who is he?

"Rumpelstiltskin is an odd fellow. Sharing traits of both wild man and witch, he is indeed a rare breed of fairytale figure. It might be said that he represents two opposing attitudes toward paganism: on the one hand, paganism can be thought of as a virtuous and more natural way of life. On the other hand, it may also be associated with a demonic or unnatural lifestyle, one that should be shunned. Rumpelstiltskin does not fit neatly into the typical template for a fairytale fiend. He is a diligent worker, honest and true to his word. He is compassionate for he shows mercy to the queen and allows her to win back her child. We can only laud his priorities and agree with him when he says: “A living thing is more dear to me than all the treasures of the earth.”

This is contrasted with the ignoble king, who loves gold above all else and only marries the miller’s daughter to enrich himself. He admits “Even if she is only a miller’s daughter, I will not find a richer woman in the whole world.”
And the queen might be quick-witted but is not necessarily a principled character. She relinquishes her first-born child because it is expedient and makes sense to her at the time."

From Fairy Tale Channel