The Deadlights were writhing, radiant orange lights that were a mysterious but very deadly and terrifying, eldritch form of energy that originated from the preternatural dimension known as the Macroverse (also known as the Todash Darkness) and a recurring plot element from the works of legendary horror writer Stephen King including The Dark Tower and Stephen King's IT. It was well known that one mere glance (no matter if a living soul stared briefly or longer) into those bright lights instantly caused death or permanent insanity.
- Crimson King: The dreaded Dark Lord, the Crimson King, wielded the Deadlights, which was also referred to as a type of magic. The Deadlights, when used, were able to cause great suffering to the point of death, and even possibly did things to the affected victim's soul. The Crimson King used the Deadlights around the once cursed American town of Derry within Maine, in the book "Insomnia" to ascend to another level of the Dark Tower, but yet never directly cast "deadlights" as any sort of sorcery himself.
- It: The very life essence and even true form of the dangerous extra-dimensional beast, It was comprised of the Deadlights themselves and used that power to blind his fresh victims (usually human children) and robbed them of their conscious minds as It drove them insane as well as left them both immobile and lifeless before It took them away and consumed them. In the 1990's TV miniseries, Stephen King's IT, in 1960, the murderous local bully, Henry Bowers, witnessed It's Deadlights after his failed attempt to kill Stan Uris of the Lucky Seven and survived, but ended up being insane while his hair was turned pale white as a side effect of the Deadlights' power, before he emerged from the sewers beneath Derry and was immediately arrested by the police for the deaths of the children taken by It, which he confessed to while in custody. Also, in the 2017 It remake, Beverly Marsh witnessed the Deadlights and was put into a temporary coma. She was brought out of the coma by Ben Hanscom kissing her. Upon looking at the Deadlights, Beverly, and, to an extend, the audience, hears sounds of children screaming, including an older person who shouted: "HELP ME!!!" This implied that the Deadlights, and, to an extension, It, did not just eat their flesh and fear, but their souls as well.