Princess Celestia is overcome with distress prompted by the wish Princess Luna granted. Celestia sets out to correct this mistake hoping the fix isn't too late.
Princess Luna reveals that a dragon's nature of greed has no place in a shared relationship with the element of generosity. Spike might have to make a choice in letting Rarity seek out another love while Generosity and fate have their own plans.
Much like the siren song from Greek mythology, the Call of the Void is always present in our minds. It is that urge to jump from a high place or into oncoming traffic. It can be made through either curiosity or despair.