The tattoo John Constantine placed on Oliver Queen during the recent episode "Haunted" will come into play fairly soon in the flashbacks -- but might not work against Damien Darhk later in the season.
Baron Reiter, who is harvesting drugs and looking for magic on Lian Yu, is the threat in the flashbacks this season -- but his magic may or may not "sync up" with that of Darhk, the season's main threat in the current day, according to one of the showrunners.
“Basically Constantine says to him that this is insurance against Reiter, and we’re going to deliver on that promise entirely,” executive producer Wendy Mericle told EW. “It’s going to help Oliver when he’s in a very dark place and time when he has no other way out. It’s going to be the thing that pulls him out of a very dark spot and literally saves him.”
Arrow returns this week as part of a two-night, two-episode crossover with The Flash. It airs Wednesdays at 8 p.m. ET/PT on The CW.