Legends of Tomorrow will see a new threat enter the picture in season two, but it might not be the obvious choice.
In the finale of season one, it is learned that the Thangarians are a coming threat, so many assumed they would be the focus of season two. According to Marc Guggenheim (via Entertainment Weekly), the show will go in a different' villain's direction, with the Thanagarian threat looming in the background.
“Unlike season 1 of Legends, where we basically had the big bad introduced in the crossover, what we’re going to do in season 2 of Legends will be more similar to what you’ve experienced in the first three seasons of Arrow or the first two seasons of Flash, where it’s more of a slow reveal and a little bit of a mystery,”
While that may mess with fan's expectations, viewers can still look forward to a heavy implementation of DC's Justice Society of America, who look to play a big part in the upcoming season. Recently Nick Zano joined the show as Nate Heywood, otherwise known as Citizen Steel. Along with Steel, Hourman Rex Tyler made his debut in the season one finale, and if those two are involved, characters like Wildcat, Dr Fate, Alan Scott Green Lantern, and others can't be far behind.