So I just saw the ultra necrozma and wondered if it may end up getting a prism card as well as lunala. Then I thought maybe it could be an evolution chain, so solgaleo - dusk mane necrozma - ultra necrozma. As the prism cards are a 1 of for each of their names, It would make it really difficult to get into play, and for anyone who's seen the ultra necrozma z-move, it is very powerful. It could also explain why the solgaleo / lunala prism cards are basics, as that would mean a lot of evolving.
Here's ultra necrozma and the z-move for anyone who hasn't seen it:
Here's ultra necrozma and the z-move for anyone who hasn't seen it: