Possible upgrades: Increase the size of the thunderstorm, increase the size of the hailstones/size of the lightning bolts, increase the pain caused by being struck.
[ Magic: Shock x Water | 'Thunder shield'; able to coat herself in a thin layer of electrically-charged ice, which when struck hurts the attacker and lessens damage to Nyx herself. ]
Possible upgrades: Increase thickness of ice for higher resistance, increase electrical charge for more pain to attacker, increase the length of time it can be maintained for.