A Dream Whisperer is an object that collects dreams of those who have forgotten them. When the person is ready, the Dream Whisperer will tell the person of the dream. It's whispers are quiet, so one who owns a Dream Whisperer must live in a quiet remote area.
At the end of the book, the Dream Whisperer told Valkyrie of a dream she had. It was when her and Skulduggery were battling Nefarian Serpine. Valkyrie had glimpsed her three names in the Book of Names, Stephanie Edgley, Valkyrie Cain and her True Name, Darquesse, the person said to destroy the world. It is revealed in Kingdom of the Wicked that Valkyrie had burnt the Dream Whisperer because she found it freaky.