| | Dark forces
The most powerfull dark entities that I have ever seen have a blackness surrounding them that looks like a starfield. My guides told me that there are always the stars with this type. The guy with the entity attached will gain power at a huge cost, that being the fact that uniting with any spirit is a trade off, as you gain power or knowledge they gain manifestation in our world via us. Eventually he would be literally at its whim, probably psychotic and definitely unable to control his destiny.