Theories on aliens.
Probability: they've mastered biotechnology.
Assumption: these creatures have biologically designed bodies, supper efficient, self sufficient (no need for sustenance), strong and basically immortal. They have the ability to transfer consciousness between bodies (as a tech, not spiritual woo-hoo), large eyes to detect multiple light frequencies, a large brain for computing/storing information, telepathy (once again, a tech). No need for most organs, maybe only need a metabolizer, no teeth, nose, hair, ear lobe, fingernails, fat, pores, but strong permanent bones. They can mind wipe humans through trauma and hypnosis. They can modify and design organisms, even entire ecosystems.
/end rambling