>>34168711It eats light. Or at least, needs it in large quantities to thrive.
Without enough light, impurities build up in Necrozma and it lives in constant pain (or goes dormant to stop the pain).
Nebby just happens to be the best snack ever. I don't think Necrozma will lose sleep over what happens to Nebby, but it's not going to go out of its way to eat your Bulbasaur for no reason either.
