A quick guide on how to get the Void ending and its achievement.
The Void ending can be obtained anytime in which you have access to the basement.
Find this paint-covered wall in the basement.
Go inside and down the stairs to find the room from the intro.
Pick up with revolver and shoot yourself in the head.
Do this 6 times until you have used every round in the revolver.
Go down and repeat a 7th time.
You will awaken at the bottom of the well from the Affliction Tape next to the apple.