A rule in hell is that every demon has to pick a person, any gender, any age. This person will have to have problems. A main problem needed is sleep deprivation. When someone is sleep deprived it is easier to reach into their dreams and appear. The only people who will ever get their 'Angel' are depressed kids. Kids that have many wrong things.

Satan has made it mandatory for a demon to complete the task of helping that child to earn its horns and tail. (If done well wings will be rewarded) the demon picks out the child at a young age, appearing to them in school and protecting them from anything bad. After the age of twelve the demon must leave to observe their persons life from hell. When the age of sixteen comes the demons have a job. Heal the scars of your person or suffer the consequences.