After defeating Necromza in its Dusk Mane Form, you will next have to go to Ultra Megalopolis in hopes of stopping it for good. As your player reaches the top of Megalo Tower where Necrozma can now be found, it will actually reach its Ultra Burst and thus will transform into its third and final form. When in this ultimate form, the Pokemon is known as Ultra Necrozma. Again, Necrozma cannot be capture this time around.
Ultra Necrozma will be at Level 60 for this battle, having the ability of Neuroforce and being a Psychic/Dragon Type Pokemon. It will also know the moves Photon Geyser, Smart Strike, Power Gem, and Dragon Pulse. As the battle begins, its aura will boost all of its stats by one stage, making for a very tough Pokemon to defeat.