Sirena is a Greek tragedy in form, since it leaves with the sad departure of Philoctetes, in the present moment from Sirena's island, but ultimately, from life itself, as he is going to fight in the Trojan War. Sirena, by her isolation and unwillingness to participate in the harmful games of her sisters, paved the way for her own enlightenment and divinization as an immortal, but unfortunately, she did not consider the fact that if the path to immortality was forbidden love, the effect might be permanent loneliness.
So in a way, the story is about many of the same titanic elements that Greek literature covers: It's about death and duty, fate one might call it. It's about love and its transient, insatiable nature. It's about the dangers of sexuality and the many pitfalls and traps we can accidentally succumb to in the process of learning what love really means, and ultimately it's about Sirena's final epiphany, that to love someone is not to possess them, but to see to it that they fulfill their destiny, even if that is not an easy pill to swallow. To have the love of your life sent of to a futile and brutal war is quite a hard pill to swallow indeed.
There is also a highly complicated archetypal story going on here, because this is not uncommon in Greek literature. There's actually an archetypal image in Sirena's character, and it has a male counterpart that would be a man whose dearest love gets away from him, but leaves him enlightened. In The Odyssey, Odysseus has a few divine girlfriends who are in the process of learning how to relinquish tyrannical control of their relationships, and the way the gods are teaching them that lesson is to send a hero who has an ultimate destiny that will rend the union between them. Sirena is another one of those kinds of stories.
