>>30403948>It's implied it only parasites you in self-defense, not to mention that the host is the one who's entirely in control.Well, entirely is an overstatement.
It's more like Nihilego removes any restraints or inhibitions they have.
>UB-01. Code name: “Symbiont.” Properly known as Nihilego. There have been sightings reported of this beast in Alola’s past. Its most distinctive feature is its parasitic capability. When Nihilego latches on to a host, it does not manipulate its actions directly. Rather it awakens the host’s own capabilities and boosts them to an extreme extent in order to protect itself.>It injects the host with a sort of neurotoxin to achieve this effect. This neurotoxin of Nihilego’s is incredibly stimulating and inspires feelings of extreme excitement and a lack of inhibition in its host. In other words, anything or anyone that a Nihilego latches on to will have its native skills forcibly activated to their fullest extent and will then act as it naturally desires to.It doesn't DIRECTLY control a person, but it makes them do things they'd otherwise restrain themselves from.
Basically, Nihilego's toxins are like drugs. Lusamine was drunk/high on jellyfish poison.