The Imposter

You are a sentient, alien, hivemind, bioweapon that consists of billions of cell size organic machines, that enters a person and seizes control of that person mind and body. You do not destroy the consciousness of the body you seize, merely push the existing consciousness to the side. They are an unwilling participant in their own body. They are effectively dead, as you cannot leave their body without destroying the body. You jump from body to body as you try and learn information that you will send back to your species for world domination.