Following the premonition of a devastating attack by Enchantress on the heroes Dove (Dawn Granger) and Deadman (Boston Brand), as well as Enchantress’ human host (June Moone), Madame Xanadu organized a team to intervene. She brought John Constantine, Zatanna, Shade the Changing Man and Mindwarp together in order to stop Enchantress.
At the end of the fight, Constantine was forced to deal with the traumatic choice between allowing the Enchantress entity to roam free and destroy everything in its path, or forcing it back into its human host, ending June Moone's chance at a normal life. He chose the latter, but at great emotional cost to himself and his teammates. As a result, when the dust cleared, none of the heroes Madame Xanadu had gathered wanted to stay together as a team.
It wasn't until days later, when the lot of them were plagued by nightmares about the inevitable fate that would befall the Earth if they did not work together, that they finally agreed to form the Justice League Dark.
Following their official formation, the JLD was immediately forced to deal with a vampire invasion (I, VAMPIRE: RISE OF THE VAMPIRES, 2012); which brought them into contact with Andrew Bennett, a vampire who was eventually recruited for the team—despite his initial reluctance. Together with Bennett, the JLD faced down a vampiric entity known as Cain, the sire to all vampires.
Later, the team was officially commissioned into action by the government agency A.R.G.U.S. and agent Steve Trevor, who officially assigned them the "Justice League Dark" moniker. In exchange for their services, Constantine was promised access to the "Black Room," an A.R.G.U.S.-controlled depository for dangerous magical artifacts.
Working from their base in the House of Mystery, the Justice League Dark was embroiled in the events of 2013’s Trinity War up to the dawn of DC’s Rebirth era in 2016’s DC UNIVERSE: REBIRTH #1.