G-Max Resonance inflicts damage and sets up Aurora Veil, reducing damage for five turns. Unlike regular Aurora Veil, hail doesn't need to be active in order for the Aurora Veil to be set up by this move. The duration of the Aurora Veil effect is extended from 5 to 8 turns if a Light Clay is held.
This article is part of Project Moves and Abilities, a Bulbapedia project that aims to write comprehensive articles on two related aspects of the Pokémon games.