Ultra Burst

Ultra Burst is Necrozma's own gimmick, and it is the longest chain on the server. Necrozma cannot use it alone: it has to fuse with a legendary first, and only then can it burst into Ultra Necrozma in battle.

Step 1: Fuse Necrozma

Necrozma fuses with either Solgaleo or Lunala, and which one decides the form you get.

You need the Necrozma and the legendary, both yours. The fusion consumes the pair into one Pokémon.

Step 2: Hold Ultranecrozium-Z

A fused Necrozma still fights as Dusk Mane or Dawn Wings until it holds the Ultranecrozium-Z. That crystal is what turns the fusion into Ultra Necrozma during battle.

Without it you get "No Ultranecrozium-Z held".

It is also what upgrades Photon Geyser into Light That Burns the Sky, Ultra Necrozma's signature Z-Move, so the same crystal does both jobs.

Battle only

Ultra Burst is disabled outside of battle on this server. Unlike Mega Evolution, which you can trigger in the open world once you are bonded enough, Ultra Necrozma only appears in a fight.

The Z-Moves of the fused forms

The fused forms keep their own signature crystals, which are worth carrying if you are not going the Ultra Burst route:

Related fusions

Necrozma is not the only Pokémon that fuses. See Fusion Items for the DNA Splicers, the Reins of Unity and the Zygarde Cube.