Rachel Lawson's The Magicians Podcast

Prince Jasper sees in a dream a monster of a man, he is a horrific man who scares him he talks to Sandy, the Neuromancer of the dream he is told the dream is the Lord of Nightmares. A mythic monster of the dreamscape. He is said to walk between the waking and sleeping worlds. He is the King of Nightmares. Known as the sleeper among the dreams. He will bring chaos to the worlds when he awakes. He is a hybrid Grim Reaper, Neuromancer, and Necromancer he is the most feared being, he is pure evil.

Jasper keeps seeing him in his dreams.