Lydia struggled mightily, with a strength that would rip a normal woman apart. But Sari was no normal woman, not any longer. It didn't occur to Lydia, when she'd initially opened the door between her energies and Sari, that Sari would discover a way to keep the door open, pulling out more power. The younger mage was more diabolical than Lydia had given her credit for. Still, Lydia was the master, and it would be simple to take control, again.
So...why wasn't she doing so?
Something about the sheer nerve of Sari's move, about feeling her full, pouty lips hungrily pulling Lydia's towards her, about the girl's weight increasing on Lydia's chest as she grew larger and stronger...it was stirring something deep in Lydia's breast. She felt her cheeks flush, her nethers grow wet...
She stopped struggling, and returned Sari's kiss, eagerly pushing more and more energy into her enlarging apprentice. Sari, for her part, was surprised, but smugly satisfied. She broke the kiss, looking down at her dwindling 'master' with cold, complete, contempt.
"Yes, that's right," she whispered, eyes wide with wicked glee. "Feed me, 'master'. Make me stronger. You love this. You're right where you belong, right where you want to be...beneath me."
Lydia nodded, shivering. "I...I..."
"Say it," Sari breathed, shivering in her own arousal. "You want to. Say it."
"I...belong to you, mistress..."
"Yes. You do. And that is why, while the rest of this world dies at my hands, you will be spared. Well, 'kept' is more accurate. Like a pet. Or a toy. And since we have time to kill before midnight...it is time to play, little Lydia."