Nick Necro was created by Justice League Dark writer Jeff Lemire.
Major Story Arcs
Years before the formation of the Justice League Dark, Nick Necro is saved from an assassination attempt from The Cult of the Cold Flame by a young John Constantine, who was looking to train in the dark arts with Necro. Initially not wanting to involve himself with Constantine, Necro agrees to train him, along with his girlfriend Zatanna. The trio would train for months, and eventually Necro would mark both Constantine and Zatanna with his rune, tattooed on their skin. Eventually, Necro became obsessed with finding the Books of Magic, the source of all magic within the universe. With Necro's attention paid elsewhere, he and Zatanna began to drift apart, as she started to fall for Constantine. Necro finds the pair kissing, and declares he doesn't care about either of them anymore, and leaves them on their own.
Sometime later, Necro contacts Constantine, asking for help, claiming that he had been captured by the Cult of the Cold Flame. When Constantine and Zatanna show up, it's revealed that Necro had begun to work with the Cult, and planned to take revenge on Constantine. Necro had not anticipate just how well Constantine took to his training, and eventually was struck by an attack that seemingly began to suck Necro's soul to hell, and despite pleading for his help, Constantine let the spell finish Necro off.
Years later, Necro, still alive, enlists the help of Felix Faust and Doctor Mist in an elaborate plan to once and for all find the Books of Magic, at the cost of Constantine, Zatanna and the rest of the Justice League Dark. The Books of Magic knock Necro and Faust unconscious. A.R.G.U.S. arrives in Nanda Parbat, where the final battle occurred, and take Necro and Faust into custody where they will be held in their underground metahuman facility located somewhere in Arizona.