In case you didn't read the summary or wanted clarification, trigger warnings for blood, mental health issues, hallucination, self-harm, martyrdom, self loathing, regression and degradation of self. I think that covers everything?
The Mistress could be good.
She had done it before when she had been he; gazing over strategies and weapons and canon fodder, calculating risks and possibilities and filling reams and reams of paper with probabilities, making the hard decisions.
The Master had been cold but oh had he been good. Fewer had died on his battlefields when he had put his mind to it, the cruel overlords disappearing into the night and a new beginning ushered in on the wings of a moth.
Sacrifices had to be made and as the most important player with the mind to get them through with the least casualties it was never him who had to fight (although they were perfectly capable of that if things got messy).
It wasn't as fun though as blowing things up, as burning and smashing and destroying things in his path but he did it anyway- wanted to prove he was better at being good than the doctor.
And he was.
But the Doctor never knew.
The Doctor didn't know about the wars he stopped because he never got called to them. He never knew about the people he saved because the people he saved never saw the Master's face.
And now he was she and she was being told to be good but his good is wrong.
His good is glory. Good people martyred in mass. Speeches about kindness and virtue and helping others.
His good hurts the people who survive. Families mourning and the wounded moaning.
His good kills more.
He loses an entire village trying to hold back an invasion which could have been thwarted before it began if he had just snuck up in his Tardis and slipped a bomb into the main generator room.
He loses children in the guerilla battleground of the biggest city on the planet he's trying to free from oppression when the cleanest way would have been to slaughter the leaders.
He holds a dying soldier's hand and he tells them they were brave and fought well.
If the Master had been here when the Master was good then village would never have realised an invasion was on the cards, the children and their families would wake up the next morning to social reform, the war would have been over before the soldier had become a soldier.
But instead the Mistress has to listen to the Doctor- has to be his good.
She doesn't at first, arguing logistics and resources and time and calculating odds.
He argues back with love and pride and kindness and second chances.
He leaves in a strop quite a few times- doesn't come back for a few days. She knows he knows that she's right really.
She's still thankful when he returns and forgets about how wrong he is a little more each time it happens.
The Mistress tries to do this until she gives in. Until she just doesn't listen, just stares blankly at him, blinking slowly.
Sometimes it's pure silence- like her mind has powered off completely and she just floats there, just existing on the edge of everything.
She tries not to think- not to imagine all the people she's scarified to save more.
It's a greater good- the amount of good, innocent people left is greater. That's what it means- isn't it?
She sits in silence, ignoring the clawing of her mind as it digs trenches in itself, brings back old nightmares which eat at her.
But she still knows deep down that she was right. She saved more people. She did good.
So she drifts in the silence.
The Mistress doesn't realise how far she's gone until the Doctor disappears for a month and comes back and she hasn't moved.
She can't speak for a few days. The Doctor helps her move about, gets her mobile again. She can't focus properly but he fixes her up, ensures that Nardole's been leaving her food and water- he had, she just hadn't paid attention- and just sits beside her, still spinning his tales of courageous good and the power of redemption.
At some point she begins to listen.
A distant part of her mind is aware that it's wrong but the Doctor keeps saying he's right and surely he must be? Nardole says he's right- and yes, the intelligence of the egg man is debatable- but it's all she has to go on.
The Doctor says he is right- knows what good is.
Nardole says the Doctor is right- is good.
So the Mistress remembers all those names of people she sacrificed. Those bodies which piled up.
It's good isn't it if she cries?
She doesn't think of all the lives she saved- never bothered to do any counting after she'd run the statistics.
She could have saved more, couldn't she?
The Mistress thinks of the corrupt who she killed without mercy.
They deserved a second chance, didn't they?
She was bad at being good- good gives chances. She destroys.
If she had given more- if she had stopped for a moment- if she had fought in the front lines- if she had given the choice.
If she hates herself that's good. It means she's getting better. It means she wants to be better.
Does the Doctor see it? Does he see how much she hates herself? Does he see her crying over all the lives she couldn't save? Does he see her nightmares?
Does he see she's turning good?
He leaves for half a year and the Mistress can feel his mind.
He's still on Earth.
She must have done something wrong- she must have been bad- she's trying not to be bad- she's trying to be!
The Mistress looks down at the blood over her hand, icy slivers of pain running off her mind like water off a duck's back- ducks, it's been so long, what do they look like now?
Blood runs down to her elbow, dripping carefully to the floor. She watches it. There's slivers of glass stuck in her knuckles.
Is this good?
She can't decide.
Her fist clenches and bits of glass- more glass, there's a lot already on the floor which shows her reflection fractured in a pool of blood- falls tinkling to the tiles.
She's drowning in it.
Her reflection is drowning in blood.
It's not hers though. Her blood was never spilled. She used other people. It's not her blood.
She's bad- awful- how could she do this.
There's a keening noise in her ears and she shrieks, gripping at her head. Flashes of light and sound. People die again and again and again and she's drowning in blood and it's everywhere- it's everywhere. Someone's screaming out in her madness of shellfire and they're louder than the rest- closer- where are they- she can't find them.
She hits the ground as an explosion goes off, arms shielding her face from the impact. Her eyes shoot open as she lands and a mad woman stares her back, face shattered with blood over her hands as she screams and she's found the woman and maybe she can be good- can help- she can do something can't she?
She recognises that face- those red lips stretched thin as she sobs and those blue eyes, pupils wide in horror, there's glass in her hand too, it's bleeding, she recognises the glass.
It's her.
The Mistress collapses over the toilet and retches, tears streaming down her face.
She's trying to be good.
She's trying to be good!
Why can't she be good?
The whine is back in her ears and she feels a dull impact as her head drops.
She awakens over the toilet bowl.
There's blood everywhere.
She cleans it up.
That's better.
She can learn to be good.
There's no glass in her hand when she's finished but when she moves her hand she can feel the stretch of damaged tissue trying to knit itself back together.
It hurts she notes idly.
That must mean it's good. Being good hurts. The Doctor said so she thinks.
Things break but she repairs them.
She's not quite sure how they break. It seems like she wakes up and there are more cuts to heal and more things to fix.
Fixing things is good.
She takes longer to fix and her body isn't as good at it as she is- there are tiny white flecks all over her now. The furniture looks as if no one had touched it.
She hears the Doctor returning. She feels the hum of his mind as it gets closer and closer.
She's been good!
She must have been- he's coming home! He's coming back to teach her more- to make her good!
She's going to be good- as good as him!
She upset the Doctor again.
His companion- the not egg one- understood her though and the Mistress wonders why the Doctor was upset.
It's bad she did but the Doctor has told her that being good is being willing to sacrifice yourself and sacrificing herself will never solve an invasion by the Monks unless she had let them in.
She only told the companion what the Doctor had told her. If the companion had died it would have fixed everything.
Somehow that's bad.
She'll try to be good.
She's trying to be good.
The Doctor checks over her that evening.
He's gentle as he traces over all the little white lines. He cries, lips trembling as he looks until her eyes and holds her arms like he's afraid she'll leave.
"Missy- this is not good. Please- please- don't do this ever again! It's bad to do this to yourself- you can't! Please!" He begs.
The Mistress looks at her arms.
She nods.
"Okay." She says quietly.
He holds her close and kisses her and she isn't sure why but she's happy so she wraps her arms around his neck, pulling him into her chest and stroking at the back of his head. The Doctor sobs against her skin.
"Teach me how to be good." She requests.
The Time Lord only cries harder.
"I don't know if I can!" He moans.
"Okay." The Mistress says. She closes her eyes and cries silently, face hidden from him.
The Mistress comes face to face with her past and he is bad.
He dances with her and kisses her and whispers that the Doctor is wrong and it's beautiful to feel right for even a moment- even if it's a lie by someone who is evil. Even if its him lying to herself.
She kills him.
She hopes the Doctor knows that she sacrificed herself.
She's a martyr now and martyrs are good as long as it's her.
He even killed her too. She doesn't know if it'll be permanent- expects it won't be.
She's still thankful- she wants to be better. Maybe her next regeneration will be enough.