Answer:
The person who makes it has no need for it. The person who purchases it does not use it. The person who does use it does not know he or she is. What is it?
I wear a red robe, with staff in hand, and a stone in my throat.
Thirty white horses on a red hill, first they champ, then they stamp, then they stand still.
Slayer of regrets, old and new, sought by many, found by few.
The man who made it didn't need it. The man who bought it didn't use it. The man who used it didn't want it.
I am used for light yet I am solid. Without me you would feel enclosed. I hate being touched especially with a lot of force. I like to be in buildings.