Use archaic and old-world methods to take care of your headache

You pay a crazy old doctor to drill a hole in your skull to let out the evil spirits. Not surprisingly, you die a horrible bloody and painful death.

Rather, what you thought of as "you" died, but in fact that was never you. It was merely a shell that you, the evil spirit, was inhabiting. You have been released, and now you are free once again to torment the living. Mostly by inhabiting people's skulls and giving them headaches, or taking them over completely and becoming an error-slaying adventurer for so long that you forget you were anything else.

You attempt to torment the crazy old doctor, but it turns out his skull is so full of evil spirits already there's no room for you as well.

You search around, looking for the perfect victim. There is a time when people are especially susceptible to being inhabited by an evil spirit. It is when they stare at a screen for too long. That's why people get headaches when they look at screens for too long, evil spirits get them.

You find an incredibly bored man who has been staring a some dumb website for hours and hours. The perfect victim. You slip through the crack in his hippocampus and make a nest for yourself in his medulla oblongata. Now what?