I do not know the context of the scene in which he asks someone from the audience to sign their soul to Satan (by coming up on stage with a picture of their loved one). Use discernment.
Acc. to Wikipedia:
Derren Brown (born 27 February 1971) is an English illusionist, mentalist, hypnotist, painter, writer, and sceptic. He is known for his appearances in television specials, stage productions, and British television series such as Trick of the Mind and Trick or Treat. Since the first broadcast of his show Derren Brown: Mind Control in 2000, Brown has become increasingly well known for his "mind-reading" act. He has written books for magicians as well as the general public. His caricature artwork has received gallery exhibition and is available in a single volume documenting his portrait collection.
Though his performances of mind-reading and other feats of mentalism may appear to be the result of psychic or paranormal practices, he claims no such abilities and frequently denounces those who do. Brown states at the beginning of his Trick of the Mind programmes that he achieves his results using a combination of "magic, suggestion, psychology, misdirection and showmanship". Using his knowledge and skill, he appears to be able to predict and influence people's thoughts with subtle suggestion, manipulate the decision-making process and read the subtle physical and psychological signs or body language that indicate what a person is thinking.
Awareness is everything.
We are Many Lights.