This is its form while it’s devouring the light of Lunala. It grasps foes in its giant claws and rips them apart with brute force.
– Pokémon Ultra Moon Pokédex
Necrozma assumes the Dawn Wings form when it takes over Lunala with the N-Lunarizer and absorbs Lunala’s light. It’s the box art legendary for Ultra Moon. It takes Lunala’s typing of Psychic/Ghost, a type combination shared only by Hoopa Confined.
Before the game came out, just looking at the box art for Ultra Moon, it looks more like a Lunala form than a Necrozma form.
Its stats change in this form. It gains 80 BST and the distribution changes. Dawn Wings form focuses on Sp Attack and Sp Def, but it’s relatively slow.