Darklings are creatures of human nightmares. They created the blue-time to hide from humans after humans started to hunt them back. They are described in the first book to behave like wild animals, only hunting people to eat and hunting the midnighters only when provoked until Jessica Day moved to Bixby, Oklahoma. They targeted her knowing she was their greatest threat.
The more obvious darklings, or the ones mainly seen are the younger ones who are like eager teenager when compared to the Ancient Darklings, who have patience to get what they want. Melissa once felt their presence which seemed to greatly terrify her from their age or power.