Most of Nanoha's attacks consist of emitting some beam or ball of energy through her body or Raising Heart and firing it at the enemy. For instance, here's Divine Buster:
Presumably she just uses her own magical energy for this. But Starlight Breaker is an exception to that. The energy seems to gather up and fire at the energy from thin air. Different versions depict it differently, but it always seems like the energy isn't coming from Nanoha directly (except the little bit that she uses to initiate the attack). Here's the movie version, it's especially apparent in the upper left corner:
Is this just a visual quirk of the attack, or does it actually work differently from her other ones? And if so, where is all that energy coming from?