From the moment Hourman Rex Tyler appeared in the Season 1 finale of "DC's Legends of Tomorrow," bringing with him a dire warning and the promise of the Justice Society of America, fans have speculated which DC Comics heroes might form its ranks.

Well, today we learned three of them.

This afternoon at Comic-Con International in San Diego, it was revealed by executive producer Marc Guggenheim that Hourman (played by Patrick J. Adams), Commander steel and Vixen will be joined by Obsidian, Stargirl and Doctor Mid-Nite. The three new roles are yet to be cast.

Doctor Mid-Nite was a safe bet, as the first hero to bear that name joined the Justice Society shortly after its 1940 comic-book debut. An excellent combatant with the ability to see in the dark, he uses blackout bombs to blind his foes.

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The son of the Golden Age Green Lantern, Obsidian was introduced in 1983's "All-Star Squadron" #25, and joined a modern incarnation of the Justice Society in 2007. He can merge with his own shadow, allowing him to fly and pass through solid objects, and possess the shadows of others.

The newest of the three characters, Stargirl was created by DC Chief Creative Officer Geoff Johns and introduced in 1999's "Stars and S.T.R.I.P.E." #0. Armed with cosmic staff, she can fly, levitate objects and manipulate energy. Stargirl previously appeared in live-action as a member of the Justice Society in the 2010 "Smallville" episode "Absolute Justice," written by Johns.

Thanks to "Legends of Tomorrow" star Caity Lotz, we learned this week that the Justice Society will debut in the second episode of the season, which kicks off Thursday, Oct. 13, on The CW.