Repulsive Hindley is a nightmare spirit in BLACKSOULS 2 that will invade you at a certain part of the Slaughterhouse area.
If you find a dead end with a corpse and if you decide to search it, you should see a red advice mark appear a little bit away from it – the message it contains will mock you for rummaging through corpses, and then Repulsive Hindley will invade you.
If you don’t see the red advice mark then you probably have the setting turned off, you can turn it on by choosing to see advice in skills. Without interacting with it he can’t invade you.
When the nightmare spirit initiates a fight with you, you will be fighting Repulsive Hindley, and Repulsive Brady at the same time. Killing them will give you the Ring of My Struggle, which increases all parameters at the start of combat.