Still being battered and pierced by Twilight's spells, Nightmare Moon hissed as she forced herself back. Her magic switched from trying to defend herself to merely trying to keep Twilight at bay, possibly harm her. She didn't have the means to block everything thrown at her at that point, and she knew she could survive it all. Bolts of magic began to pierce through her flesh and shatter her bones as new tissue still grew to replace the damage one, her wounds leaking not just blood but mauled chunks of muscles and organs as her skin kept regenerating and being torn apart at such a rate that the edge of her body started to seem liquid more than solid.
Whips of blue flames spurted from her horn to strike towards Twilight. Twilight stepped back and swatted them away with the blade of light on her horn, while her secondary spell continued to shower Nightmare Moon with dozens of sparks. She sliced through the flaming tendrils, and in doing so sent golden pulses of electricity riding along the remaining length of them towards Nightmare Moon's horn. As soon as she noticed that, before they could reach her, Nightmare Moon undid the spell, and switched to a different one.
A series of small, miniature moons flowed from her horn, no larger than a pony's head, and they all began to head towards Twilight. Recognising them for the mines they were, Twilight immediately adapted her strategy. While she bent the branches of her maintained spell so their projectiles would circle around the incoming attack, she produced a wave like a sound from her horn, gold and purple, contained within the space in front of her. It undid the magic within the spherical projectiles into harmless energy, and crushed them into ethereal dust. Twilight advanced, and Nightmare Moon was forced to retreat and rethink her plans, as her body remained battered and barely protected by shields she'd put up to her sides and was not maintaining.
Another lightning struck, more brief than the previous one, and it burnt through Nightmare Moon's uncaring flesh. One of her eyes melted and leaked sizzling down the side of her face, and immediately a new one was there to replace it, filled with even more hate. Baring her fangs, even more so than regularly possible thanks to the missing patches of flesh on her face, she abandoned almost all restraint and shot forward a single torrent of magic from her horn.
That did force Twilight to abandon all other spells as she fought against it. But as the four branches of her magical chandelier condensed into a single wide beam of lavender gold, not only did she stop the deep blue waterfall of Nightmare Moon's attack, she began to push back against it. Between the unhinged powers of two alicorns in her and Nightmare Moon's own magic still half focused healing her body, it became clear Twilight stood a real chance at fighting back against the other.
Nightmare Moon, her neck tense and her teeth clenched, was forced to step back and farther back still, up and up the broken crystal tower as she struggled to prevent Twilight's spell from overpowering hers. But if she could hold on long enough, as soon as her body was done regenerating she could attempt to overpower the younger alicorn, she reasoned. That was when another, much more physical bolt struck her, and she found herself impaled side to side by a crystal shard the shape of a stalactite and the size of an umbrella.