Take a look atSeason 4 of The CW's "Legends of Tomorrow", set in the 'Arrowverse', as a spin-off of "Arrow" and "The Flash", premiering October 22, 2018:
"...after killing the demon 'Mallus', the 'Legends' were ready to relax until 'John Constantine' informed them that, in solving one problem, they created a much larger one.
"When the Legends let time crumble to release and defeat Mallus, the barrier between worlds softened. History is now infected with 'Fugitives' – magical creatures from myths and fairy tales.
"Having been expelled throughout time by people like Constantine, they are now returning to the real world in droves and making a mess of things..."
Click the images to enlarge and Sneak Peek "Legends of Tomorrow" - Season 4...