"Octavia!" the Doctor said happily as he sifted through Octavia's sheet music. "If you can hear me stamp your hoof once!"
Octavia did against the Mara's will. "Stop it!" the Mara hissed. "You gave me control of this body, and I intend to keep it! There is no way I'm giving up now!"
"Oh, surely not," the Doctor smiled. "That would take the presence of mind to know when to quit, something you, with your primitive reptile brain, have never been able to grasp... No, that wasn't fair. I just threw Silurians and Ice Warriors under the bus with you..."
"You think I'm going to let you just keep mocking me like this?!" the Mara shot back.
"Yes," said the Doctor matter-of-factly. "Octavia, dear, haven't you written anything a little less gloomy? This is all very beautiful work but I need something upbeat if I am going to fully get you out of this in any sensible amount of time. Oh, one tap for yes, two taps for no."
Octavia's hoof tapped once. The Mara hissed in anger.
"Ah, lovely," the Doctor said. "When you're ready, give me the title. Shouldn't be long until you get control of your mouth again, in the meantime we will all have a round table discussion with the talking belt."
"Oh, wow," Blue smiled. "This is priceless."
"Now, young man," the Doctor said sternly. "I do not condone taking abject pleasure in the suffering of others."
"Neither do I," Blue said defensively. "That being said, when the subject of the schadenfreude is a being who exists on torment, and has been harming you and the ones you care about..."
"It's hard to control, yes," the Doctor frowned. "That baser instinct to smile when crushing your enemies... How very Sontaran of me. I must keep watch on that."
"You haven't won yet!" the Mara screamed.
"Yes I have," the Doctor said immediately. "The moment Ms. Scratch came through the door with that cello."
"Yeah, about me," Vinyl said shakily. "What do I do? How do I get Octy out of this? I don't wanna see her get hurt!"
"Start there," Applejack said, catching on. "Start there and keep going."
"Give miss Applejack a round of applause!" the Doctor said happily. "Positive emotional energy to combat being of negative psychic responses. Normally it would take much more than this to harm you, but you've obviously been weakened significantly over the past ohhh... Twenty-Four hours. Am I right young man?"
"Twelve," Blue corrected.
"That must have taken an enormous boost of positive energy to weaken the Mara in such a short time," the Doctor raised an eyebrow.
"A thing happened," Blue said awkwardly. "I took care of it... Modesty forbids me to say it was that good- This is getting weird, back to Vinyl."
"My friend is in pain!" Vinyl protested. "You're saying I can fix it, but I don't know what the hell I'm supposed to do!"
"You've already done it," the Doctor said quietly. "You stepping in this room has given Octavia the will to fight back. That's what you've always done for each other. I heard those stories. Being enemies in kindergarten thanks to different tastes in music. You standing up to bullies that picked on her for her accent. Her taking you in when you had no where else to go."
"You want me to kill an alien snake monster," Vinyl asked angrily. "With the power of friendship?"
"Don't knock it 'til you try it, Sugarcube," Applejack said smugly.
"What would life be like without her in it," Blue said. "Think."
"I literally can't imagine that," Vinyl snapped back. "I won't. Simply put, in my head that's an impossibility. She's been there for me so often that... Look, she's family. She is the only pony in the world I consider family. She's been so great all my life that I owe her that same kindness."
"You never owed me anything," came the correct voice from Octavia's body.
"Octavia?!" Blue said.
"No!!" the Mara hissed. "No get bac-"
"You get the hell out of my friend!!" Vinyl shrieked.
"Temper, Ms. Scratch," the Doctor smiled. "Catch more flies with honey, remember. We were getting farther the other way."
Vinyl looked at the Doctor, then back at Octavia. She finally understood what she had to do. "Octy," she said to her friend. "I don't say this often enough... But every memory that's worth having includes you. If it weren't for you, I probably would have burned out in a drug fueled haze a long time ago. You set me straight without making me boring. And even though I make fun of you sometimes, I love what I hear of your music! I may not get it, but it really does sound so beautiful to me. You are the one pony I can genuinely say I look up to."
"She can't hear y--" The Mara's neck craned. "Yes I can," Octavia said. "And if you think I'm ever going to let you live that down, Vinyl Scratch, you're delusional!"
"Would expect nothing less, you Trottingham Troll!" Vinyl let out a huge grin. "You back for good?"
Octavia's neck craned again, her eyes glowed a bright red and she let out a monstrous hissing noise. She then craned her neck again. "Not quite," she breathed heavily. "Endless Forms Most Beautiful."
"A quote by Charles Darwin?" the Doctor asked.
"My happy song," Octavia strained. "It's called 'Endless Forms Most Beautiful.'"
The Doctor searched through the sheet music until he found what he was looking for. "Ah, yes," the Doctor smiled. "Could you put our friend back on, I'd like to talk to him."
Octavia's neck craned again. "Do you think a little music is going to stop me?!" the Mara hissed.
"Haven't you been listening?" said the Doctor as he set himself up around the Cello. "You've already lost."
"I doubt that," the Mara shot back.
"Then why are we still talking?" The Doctor began to play. "See, that's the thing... If you had full control over that body, you;d be wrapping those hooves around my throat right now. But you're not. And you won't. Because you were right. Evil is mundane. It's everywhere. Matter of fact, one might call it common.... Oh dear me, I have become an upper-class twit, haven't I?"
"That's a change?" Applejack asked.
"Hush, you," the Doctor frowned. "Good, however, is exceptional. It takes time and energy. And quite a fair bit of thought. Listen to this piece..." The Doctor continued playing Octavia's music. "I'm doing the bit for the strings, but there are other parts... Bits for guitars, drums, it even calls for some electronic elements later in the work... It all comes together in a sort of..."
"Harmony," Applejack finished.
"Quite," the Doctor smiled. "This piece seems to be an ode to music itself... Blending classical sensibilities with electronic techniques... I wonder where she got that idea." He winked knowingly at Vinyl.
"Oh, Octy," Vinyl was tearing up. "Wow... Just..."
"I think I understand the title," the Doctor smiled, as he continued playing. "Its a quote. Said about life on earth, but it works for music as well. 'From so simple a beginning, endless forms most beautiful and most wonderful have been, and are being evolved.' Good man, Charles. A bit obsessed with his finches..."
"What does this have to do with anything?!" the Mara hissed.
"'Most beautiful, and most wonderful,'" the Doctor repeated. "That man posed the hypothesis that we all struggled for survival. So much death, and so much pain. All life crawled screaming from the muck... But still, he saw life as a beautiful thing. That takes a spirit that is truly inspiring. The made you're squatting in has that same spirit. And that's why, in a few measures, she's going to beat you."
"PLEASE!!" the Mara spat. "Despite what you told the green maned idiot, there is no such THING as a happy ending. I am the voice in EVERYPONY'S head! I am the natural end to all things! At the end of it all I. ALWAYS. WIN!!! Whatever you think you've got..."
"What I've got," the Doctor sighed, placing the bow to the side. "Is something you don't know..."
"What?!" The Mara snapped. "What do you think I don't know?!"
"I'm rubbish with a Cello," the Doctor smiled. "Octavia!!!" The Doctor spun the cello over to where the Mara was standing...
And Octavia deftly caught.
The Doctor walked calmly over and placed the bow in Octavia's hoof. "I believe this is yours, dear lady."
"Thank you, Doctor." Octavia then began to play. With the hooves and skill of an expert music filled the nightclub until it was all anypony could hear. This music meant so much more than just a piece she would perform. She was playing for Vinyl, and Applejack, and the Doctor, even that poor stallion Blue. She did what music did best.
She lifted spirits.
The mark on her left foreleg faded rapidly, and the Spectral form of the Mara rose out of her back. "This isn't the end, Time Lord!!" The Mar seemed to writhe in pain. "I'll keep coming back!! Always! You haven't seen the last of me yet!!!"
The Mara began to laugh.
Then the Mara began to sing.
"Christ rose on easter morning,
Mary and Martha came down to see,
He said "Go tell My desciple.
To meet me in Galilee..."
And then the Mara dissipated. Gone from the room.
Shortly afterward, Octavia collapsed