You could see the potion that Circe gives Glaucus as being symbolic of the destructive power of love. Circe tells the sea god that it's a love potion guaranteed to make the beautiful sea nymph, Scylla, his forever. Glaucus swims toward his reluctant love, hoping that his future will be full of happiness. Unfortunately for Glaucus and Scylla, the potion is really meant to transform Scylla into a horrible monster. Though the potion was requested as an act of desperate love, it instead ends up destroying Glaucus' object of affection. You could also see the potion as embodying what happens when true love is mistaken for obsession.