Nightmare Moon barely had time to turn around as another chunk of smooth pinkish crystal, not dissimilar from the first, sailed through the sky at blinding speed and pierced her torso, crushing her ribs and tearing through her veins. As she looked towards the alicorn responsible for that, a third projectile was fired and it hit her hip instead, and lodged itself there.
Starshine didn't stop firing. She only grew more skilled at it. A fourth shot fired just moments later broke Nightmare Moon's spine in half, then one reached her throat and neck, then two more on her belly, one piercing her wings as well, and one on her shoulder, as Starshine began to shoot so quickly she had to keep up a gait, each crystal generating before the previous one had been shot off forcing her to move forward for each new shot she wanted to fire. She showed no signs of stopping either, and Nightmare Moon caught in horror a glimpse of her readying dozens of bolts to fire in sequence.
Those never reached the alicorn's body. Shot after shot sustained Nightmare Moon's ability to keep up her spell was failing her, as more of her magic had to be diverted into healing her wounds. It became clear to her then that whatever Luna had done, she hadn't merely forced her to heal. Twilight was powerful, but she wasn't absurdly powerful enough to justify what was happening. Nightmare Moon realised, perhaps too late, that her powers were not answering her properly, as if along with the wound Luna had left on her a block of some kind that prevented her from controlling them in full.
One shot reached the back of her head, shredding what was still there of her helm. Just a moment of hesitation too much, a split second where she wasn't focused. Twilight's spell gained on hers and there was no stopping it afterwards. It came onto her like a flood, swallowing her body whole and swallowing those crystals Starshine had been shooting towards her along with it. Past her and towards the sky, a beam not too unlike the one that had destroyed the tip of the tower they were on.
Twilight pushed on with her spell, a horn that should have been burning from the sheer amount of energy being poured through it kept safe only by yet more energy being diverted into maintaining it stable and safe. She couldn't sense Nightmare Moon's body within the torrent of her magic, but she knew the alicorn couldn't teleport away. If she'd tried, the spell itself would have kept her trapped there, just as magic had kept her from escaping on her previous attempt.
Her stream of gilded violet soared towards the sky, piercing through what clouds it found along the way, and for a few moments longer Twilight kept on with her outpour. Then, choosing it was enough and beginning to feel the strain of her efforts for the first time since being blinded by rage at the sight of Luna's body, she allowed the flow to die down, and kept herself ready to use her magic again as soon as she may have needed to.
Nightmare Moon still stood there, a surprising feat for only half of a body. Despite that, as soon as the portion of her face still present had an eye again it glared at Twilight with hate. New bones jutted outwards for her flesh to regrow around, and Twilight flared her magic again, going for another strike.