Despite defeating her dark side, Luna's shadow appears in "The Descent."
In this, Shadow Luna looks like a black, bloody, humanoid monster with a bloody, toothless mouth and beady eyes that glow in the dark.
MAJOR SPOILER WARNING!
Are you still here? I suggest you don't read this, as this spoils a LOT for "The Descent"... As I was saying, this represents Luna's desire for revenge against Revelian, due to the fact that he murdered her some time before the events of "The Descent". The blood on her body represents how she died: Revelian beat her violently, knocking all of the teeth out of her mouth. He then raped her, and cut her heart out with his sword. As the opposite of the element of "Love", Shadow Luna is cold, violent, and hateful. She also represents how the truth can be very frightening: While Revelian denies and locks away what he done, she is shadowy and incomprehensible. But when he starts to realize the truth, she reveals her true form, which is herself, only naked and violently distorted- Her fingers are gone, and replaced with long, sharp blades. The nudity represents how Revelian started to view her at the end of his marriage: A simple sex thing. At one point, Revelian witnesses Shadow Revelian violently beating Shadow Luna. In this scene, Shadow Revelian's voice is low pitched and almost a roar, where Shadow Luna's voice is high-pitched and whiny. This represents how Revelian's marriage soon became after the child died, and how Revelian viewed Luna at the end of their marriage- A whining, obnoxious bitch. Revelian, at the end of "The Descent", finally gets in a final confrontation with Shadow Luna. He nearly dies to her, and while he lies on the ground, near death, he remembers all of the good times in his life and begins to actively feel regret for what he's done. Seeing how he has finally repented for his sins, Shadow Luna releases him and allows him to live. Before fading away, her appearance changes back into her normal self, only bloodstained. She gives him a final kiss before finally fading away. He leaves the building, where he ends up in a shadowy pier like area. He crosses a long bridge and winds up in a small room, where Luna lies on a bed. She forgives him for what he's done personally and finally dies. It's here that Shadow Revelian offers the real one a last chance at redemption. He takes it, and heads back into the past to make things right.
In the Joke Ending, Shadow Luna winds up just being Luna, just covered with blood and wearing "fake eyes". She apologizes to Revelian for being rough, saying "I had to stay in character". She then runs everyone else out so she can "make it up to him". And then Luna and Revelian had lots of sex cause.