Technically, viewers were introduced to Vandal Savage (Casper Crump), the season 1 villain, before an actual episode of Legends of Tomorrow ever aired. The CW introduced the spinoff series in a two-night crossover event on The Flash and Arrow. A concept that was originally supposed to happen with The Flash ahead of its first season, but CW scrapped the idea of a back door pilot after Grant Gustin's guest appearances as Barry Allen on Arrow tested so well with audiences.
Legends of Tomorrow has already revealed that the Justice Society of America will be a major factor in their second season. They've also announced that a version of Vixen will be a series regular, and we now know that Dr. Nate Heywood a.k.a. Citizen Steel (Nick Zano) will be joining Rex Tyler a.k.a. Hourman (Patrick J. Adams) and, more than likely, Jay Garrick (John Wesley Shipp) as JSA members. Bringing in the JSA opens the door for a host of big bads to give our new band of time travelers some trouble. Even though Savage himself dropped hints at a future Thanagarian invasion, Legends producers have someone (or something) else in mind.
Marc Guggenheim recently teased the season 2 villain in EW's Spoiler Report:
“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.”
Legends of Tomorrow's first season trudged through an uphill battle to find its footing, and Vandal Savage was a contributing factor. The problem wasn't that he was introduced too early, per se, but instead that there was too much backstory and history between characters for whom the audience had yet to form an attachment. Kendra (Ciara Renée) and Carter (Falk Hentschel) had 4,000 years to learn to hate Savage, yet audiences had no ramp up for such disdain. It seems that fans haven't gone unheard, and the producers and writers for Legends of Tomorrow are working toward a course correction for their sophomore season.
At CW Upfronts, cast members implied that season 2 might have less traveling from one time period to the next week-to-week. Brandon Routh even teased that fans could see multiple villains throughout the season to provide some variety instead of the constant chase of just the big bad.
Legends of Tomorrow returns to the CW on Thursday, October 13th at 8pm ET. One week earlier, both The Flash and Arrow premiere on Tuesday October 4th and Wednesday October 5th, respectively, in the same timeslot. Supergirl makes her CW debut after Legends on Monday, October 17th at 8pm ET.