Supernatural is a TV show that began in 2005 on the network known as The WB. The show's life was in the balance when the network merged with another and became The CW. After two successful seasons on the air and a huge fan base developed, the creator Eric Kripke launched the comic. The comic series is a prequel to the show and is titled Supernatural: Origins.
John Winchester's wife Mary is killed in an unusual magical event by a yellow-eyed demon. John is left with the task of raising Dean Winchester and Sam Winchester but at the same he is too obsessed with finding and killing the demon. He enlists the help of Missouri Mosley, a psychic in Lawrence, Kansas. In issue #1 of Origins, Missouri and John are able to have time alone for spellcasting while the boys are in the care of their mother's best friend. Missouri extracts a whole fingernail from John as a sign of his sacrifice. Her visions show her a scene which includes a description of a house and the street names. When Missouri and John arrive at the house, they are too late. The blood on wall reads, "We're coming for the children."
John assumes the message is about both of his children. He and Missouri take off to find the boys at Julie's house. They find the house splattered with blood, no sign of Julie, but the boys are okay. As John gathers the boys to leave, Missouri hands him a long bluish fang covered with markings. It appears to be the first magical item John holds in his possession. Missouri instructs John to find Fletcher Gable in a town called Eureka.
She's mentioned in issue #2 only by name. The extent of her abilities are not fully known. She's a palm reader, psychic, and spell caster, she can also hear surface thoughts. That just might mean that she other abilities such as psychometry, illusion, hypnosis or necromancy even if she chooses not to use them.