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...