Pokémon Sun and Moon - Mother Beast

Nihilego is interesting g even by ultra beasts, it feeds off negative emotion it’s venom causes. And it isn’t the only depicted ultra beast that can fuse itself to a human host, could nihilego combine to anything with emotions? Or does it only target those full of them to begin with. Could it fuse with a Pokémon, or even another ultra beast? Poipole is said to understand emotions after spending g enough time around people.. could a nihilego attack itself to a poipole and become stronger?

Oh hello there darkness, I didn't see you there