Does "which have engaged..." refer to " haunted houses" or does it refer to all of them?

Does "which have engaged the attention of mankind at every epoch of history" refer to " haunted houses" or does it refer to all of them?

In this unhappy wandering class lies the explanation of all those ghosts, spectres, apparitions, and haunted houses which have engaged the attention of mankind at every epoch of history.

"The History of Spiritualism," by Sir Arthur Conan Doyle