The Arrowverse crossover’s latest addition is a real psycho: Bob Frazer will guest-star during the three-night “Elseworlds” event as Arkham Asylum inmate Roger Hayden, TVLine has learned.

In the DC Comics’ Prime Earth universe, Hayden was known as Psycho-Pirate, a member of the Secret Society of Super-Villains who wore a Medusa mask that could manipulate emotions. The mask eventually drove Hayden insane. The Flash‘s Season 5 premiere made reference to Hayden/Psycho-Pirate, who is quoted in Iris’ article about the speedster’s disappearance in the future.

“Research has focused on Roger Hayden, a.k.a. Psycho Pirate, who claims to remember the night’s events,” the article says. “He said upon his arrest, ‘Worlds lived, worlds died. Nothing will ever be the same.'”

Hayden will appear in the Arrow and Supergirl episodes of the crossover, which kicks off on Sunday, Dec. 9 with The Flash (airing on a special night). The event will continue on Monday, Dec. 10 with Arrow before concluding on Tuesday, Dec. 11 with Supergirl (airing on a special night). Additional guest stars include Ruby Rose (Orange Is the New Black) as Batwoman/Kate Kane, Tyler Hoechlin (reprising his role as Supergirl‘s Superman/Clark Kent), Elizabeth Tulloch (Grimm) as Lois Lane, Jeremy Davies (Lost) as Arkham Asylum doc John Deegan, LaMonica Garrett (Designated Survivor) as Mar Novu aka The Monitor and Cassandra Jean Amell as Mr. Freeze’s wife, Nora.

Frazer’s TV credits include guest spots on The Man in the High Castle, The 100, Falling Skies, Supernatural and Flash Gordon.