It's 7 forms tie all generations together into 1...

1 Necrozma Fragment Form (Normal Form. Psy Type)

2 Necrozma Gene Form (+Mew. Psy Type)

3 Necrozma Prism Form (+Ho-Oh. Psy/Fire Type)

4 Necrozma Ascension Form (+Rayquaza. Psy/Dragon)

5 Necrozma Origin Form (+Arceus. Psy/Normal)

6 Necrozma Completion Form (+Kyurem. Psy/Dragon)

7 Necrozma Guardian Form (+Zygarde. Psy/Dragon)