WARNING: Contains SPOILERS for Arrow, season 8, episode 2, "Welcome To Hong Kong."
Arrow season 8, episode 2, "Welcome To Hong Kong," ended with the revelation that Lyla Michaels, director of ARGUS and John Diggle's wife, was in communication with the Monitor and aware of the coming Crisis On Infinite Earths. This was something of a surprise, given how secretive Oliver Queen had been regarding the impending doom of all reality and his efforts to aid the Monitor in preparing for the Crisis alone.
"Welcome To Hong Kong," found Oliver Queen, John Diggle, and the Laurel Lance of Earth-2 back on Earth-1, following the destruction of Earth-2. As a distraught Laurel went off in search of an old contact she thought might be able to help her return to her Earth, Oliver and Digg focused on completing the latest mission Oliver had been given by the Monitor. However, before the two began searching Hong Kong for a missing doctor, Digg took the time to call Lyla into action, so that Laurel would have some backup.
The final scene of the episode featured Lyla meeting the Monitor in a dark alley and admonishing him for not warning her about what was about to happen to Earth-2, saying that her husband could have been killed. The Monitor, while not apologetic, was far kinder in addressing Lyla than he was with Oliver. He noted that the sacrifice of Earth-2 was regrettable but necessary given their ultimate goals. The Monitor also noted that "countless more like them will perish if we do not ensure that Oliver Queen is prepared for what is coming."
The fact that Lyla was already communicating with the Monitor was no surprise to comic fans who had read the original Crisis On Infinite Earth comics. The comics leading up to Crisis introduced a young woman named Lyla into the DC Comics' universe, revealing her as having been raised by the Monitor as his own daughter after he rescued her from being lost at sea. As the Crisis approached, the Monitor empowered Lyla, transforming her into the heroine Harbinger. It was Lyla who took on the task of coordinating many heroes across multiple Earths in the battle against the Anti-Monitor.
It remains to be seen precisely what role Lyla Michaels will have to play on Arrow during Crisis on Infinite Earths, but it seems certain to be a big one. Photos have surfaced of Audrey Marie Anderson wearing a stylized set of armor based on the Harbinger costume from the comics. Anderson has also been seen wearing the super-suit on the set of Legends of Tomorrow, so it seems likely that the Arrowverse's Lyla Michaels will have the power to be in several places at once, as in the comics.