Summons/Legendaries

I've summoned 63/65 legendaries, but still can't seem to use the azure flute to summon arceus. I'm really confused, it's the only one I can find that I haven't already summoned?

Have you summoned all the ultra beasts as well? And arceus can only be summoned once everything else has been summoned, like ultra beasts and type: null.

Oh okay! I've got the ultrabeasts to go then and type null. Is this why I can't summon Necrozma yet either even though I have the black prism?

you do not need to hatch every single ultra beast in order to unlock necrozma, you only need to hatch all of them up to guzzlord. you'll unlock type: null at this point as well (by trading in 6 hatched ultra beasts for a type: null egg voucher).

Okay, so I just need to start on the ultra beasts, thank you both so much! Hi, sorry quick follow up on this! So I know you need both solgaleo and lunala to unlock the aether house, but does it take them? Or do you keep them?

you keep them! they just need to see them, you won't lose either of them.

oh brilliant, so i can just borrow one from another plsyer then send it back?

yep