Erlking

This line, and indeed the whole passage (lines 653-664), allude to the well-known poem by Goethe about the erlking, hoary enchanter of the elf-haunted alderwood, who falls in love with the delicate little boy of a belated traveler.

So easy for one young son to be swallowed up in a world teeming with Erlkings, real and imagined.

He was in the forest looking to see the trees / But none were there / He found a girl / She found the erlking

By now, he seems less a cartoon character than some contemporary Erlking, the malicious spirit made famous by Goethe (and Schubert) but found originally in a Danish ballad.