The Flash is dragged into a cave by Doctor Fate, who informs Wally that the two are trapped in a two-dimensional causeway and "…it's going to be up to you to guide us. To help us through." When Flash doesn't understand how he can help, Doctor Fate corrects him, pointing to the reader and shouting "YOU! The reader of this book! Our fate lies in your hands." At various points in the story, Doctor Fate insists that the reader turn the book clockwise, counterclockwise, and eventually upside-down, shifting gravity within the world of the comic. Doctor Fate and the Flash even climb from panel to panel, evading monsters on every page.

As an outside observer, the reader of comics is seldom taking action within the book. From a Doylist perspective, of course, the reader is not; the pages have been printed long before the reader ever bought a copy. Nor does the book account for a digital copy of the issue (Doctor Fate doesn't tell the reader to turn a phone, tablet or laptop, for example). Nevertheless, this is potentially one of the strongest powers in comics lore, showing that while Deadpool is content to make jokes about the meta-nature of his existence, Doctor Fate and the Flash actively use the reader to accomplish their goals.

With Doctor Fate having opened the Flash's eyes toward the fourth wall, Wally West is now aware of the world beyond the confines of his universe. The episodic nature of the current Flash run does not necessarily mean Wally will remember this encounter, however. Nevertheless, Deadpool no longer has a monopoly on breaking the fourth wall…for that honor now belongs to the Flash

https://screenrant.com/flash-weaponize-deadpool-fourth-wall-doctor-fate-marvel/