Even without her mental issues and physical weaknesses, it's no secret to Mabel Northwest (Llama) that she is Ford's least favorite ward. She's not at talented as her beloved brother and more prone to flights of fancy; it's almost like a relief to the Northwest family name when Ford finally has an excuse to lock her away from the public eye after she has a big breakdown in public. Mabel's been told that she's very very sick, but she can't help but feel that something else might be going on...
Unbeknownst to Mabel, there's a certain dream demon who has been residing inside of her head for years now because of a deal he made with her great-uncle, his parasitic presence giving her terrible nightmares and an unstable condition. The longer time goes on, the easier Bill's mindscape realm becomes for Mabel to access on her own, along with her own set of mindscape manipulation powers. However, until she realizes her full potential, she'll remain Bill's little vessel-in-training without even realizing it.