There's a ton of theories about the black eye. Three big ones, in order of weirdness:

1. being part of a ritual, illuminati beating / hazing / "jump in"

2. adrenochrome injection into the eyes. Alternatively, black eyes being adrenochrome withdrawal symptoms.

3. entry point of mind controlling vril lizards.

I'm leaning towards both 1 + 2 but would not be surprised if it ends up being "all of the above".