Magic Vs Magic
When Nabi had lifted his hand up, there was an instinctual reaction from Raze. He had seen this type of movement many times before in his past life, more than he could count. In the world of Pagna, he thought that he would never experience it, at least not here. So for a moment, he thought he might have been wrong.
His experience as a teacher, he had seen those start the spell the same way. This was a spell linked to those with the Lightning attribute. To draw more power, they often had to lift their hands in the sky.
They could still use lightning-type magic without it, but if it was a long-ranged attack and they needed to store lightning quicker, raising their hand was the ideal way, and just before Nabi had cast his magic, he had said the words of the spell.