Fix-it fic, post-"The Doctor Falls", spoilers from promotional graphics of Jodie as the Doctor, and written for the "Round" drabble challenge at who_contest.
She felt an irritating warmth flower throughout her body. She could see blackness becoming lighter under her closed eyes, and that familiar feeling of golden energy hummed like a dual heartbeat in her ears.
Missy was sure this wasn’t death or Hell, not the place where she thought she’d go at the end. She felt a laugh caught in her throat, and she wondered if it had been trapped there in that last moment when her previous incarnation killed her.
But he hadn’t.
She was breathing. She could feel the flow of time around her, and she recognized her surroundings as well.
“Elysium… heaven, whatever,” she joked wryly under her breath.
“‘Fraid not,” a feminine voice answered her. “Sorry to disappoint you.”
Missy blinked and noticed she was inside the Doctor’s TARDIS. She groaned at the flickering round panels on the wall. She took another breath and felt an ache all over her body. She felt particular pain in the region where her other self had shot her.
Slowly, she stretched and met the face of the person who had spoken to her. Short blond hair, curvier figure and most certainly, a body absent of angry eyebrows and gray hair. Plus, she noticed some other things missing as well. Her new companion cocked her head at her.
No matter how many times “she” changed, Missy recognized her friend anywhere. “You saved me.” Missy looked at her hands. Residual regeneration energy fluttered around her like dust. “You used your regeneration.”
“You’re welcome,” she said and turned away to the console, playing with knobs and trying to seem disinterested. Yet, Missy knew the Doctor was pleased with herself.
“Before you thank me, I must warn you that I didn’t entirely save you. I just gave you the ability to regenerate again.” She turned back to Missy with sympathy in her brand new face. “I’m sorry, old friend, but you’re still dying. I brought you here to the TARDIS to make it less painful.”
Missy’s words were caught in her throat, and she knew the Doctor was right when small fissures of pain in her body started to erupt. She inhaled a strangled breath. The Doctor moved quickly by her side and took her hand. She helped Missy up and propped her against the console of the TARDIS and watched her intently. Missy held onto her hand, grateful for the attention as the change began.
Her other regenerations had been so painful, so full of darkness. With the Doctor holding her, in her new form, it soothed her.
She made a move to let go, but Missy held on and pleaded with her. “Don’t leave.”
“I won’t,” the Doctor said, and Missy studied her, suddenly liking this new Doctor. “You won’t be alone, old friend. Not this time.”
“Why are you doing this?” Missy asked, wondering if she would end up owing the Doctor in the future.
“Because,” the Doctor said simply, and Missy felt her squeeze her hand. “You’re my oldest friend.”