This episode is part of a larger crossover series, Armageddon.
"Armageddon, Part 2" is the second episode of the eighth season of The Flash, and the one-hundred-fifty-third episode overall. It aired on November 23, 2021.
The episode is the second part of the five-part crossover, Armageddon.
Despero warns The Flash that great tragedies will befall the speedster and cause him to lose his mind. Once that happens, Armageddon will begin. Determined to prove Despero wrong, Barry doubles down on proving his innocence but a devastating revelation from Iris pushes him to the edge and sends him to seek counsel from Black Lightning.[src]
This episode features or confirms the deaths of two characters who have been in the show since Season 1: Gideon and Joe West.
Alex tells Iris, Chester, Allegra and Caitlin that they are the first to encounter a Kalanorian. However, a Kalanorian started a fight in Al's Dive Bar due to the psychic effect of Myr'nn J'onzz's Ta'ar Ka'riq in the Supergirl episode "In Search of Lost Time".
This could be a change caused by the fallout of the Anti-Monitor Crisis.