The CW's Legends of Tomorrow premieres in just a few weeks, but fans already anticipate that the show will get off to an epic start.

Intended as a midseason replacement for shows during their hiatus period, particularly Arrow and The Flash, Legends of Tomorrow combines characters from both of those series and creates something new: a team of outcast heroes and villains who must join together to save the world.

In doing so, this team of legends must travel through time to prevent Vandal Savage from destroying the future.

Here's everything we know so far about the series:

Main cast of characters

Many returning characters from The Flash and Arrow will appear on Legends of Tomorrow as part of the team. This includes Sara Lance, who recently got resurrected from the dead on Arrow. Once Black Canary, Sara takes on a new costume and becomes White Canary in Legends. Joining Sara from Arrow is Ray Palmer, The Atom.

The Flash also contributed characters to the team, including the recently-introduced Hawkman and Hawkgirl. The new version of Firestorm joins them: the combo team of Dr. Martin Stein and Jefferson "Jax" Jackson. The Flash also contributes two villains to the cause: Heat Wave and Captain Cold.

The original Ra's Al Ghul will also become part of Legends of Tomorrow, although it's likely the team will run into him in the past as the character is now dead in the present.

There's no word on whether any other characters from Arrow or The Flash will appear on the series, but considering how much The CW loves crossing over, it's likely.

Finally, Legends introduces a new main character, Rip Hunter. Hunter is a time-traveling rogue who assembles the team and gives them their missions.

Villains

The main villain that our team of legends must face is Vandal Savage, who first appeared on Arrow as an immortal man intent on getting revenge on Hawkman and Hawkgirl. However, Savage died on Arrow, although the final scene of that episode showed Malcolm Merlyn scooping up his ashes and saying something like "You owe me, buddy."

Of course, this is also a show with time travel, and viewers have not yet seen what Vandal was up to in the past, but it's likely that he began his plot to ruin the future for everyone a long time ago.

Arrow villain Damien Darhk also plays a part in Legends of Tomorrow, as part of a storyline that takes place in the 1970s.

"You go back to the League — I did an episode of Legends last week — and I look exactly the same in 1975 but you see he's not as confident and doesn't have such an agenda 40 years ago as he does now," said actor Neil McDonough, who portrays the villain, to ComicBook.com.

Guest stars

In addition to having actors from The Flash and Arrow appear on the series, Legends recently began teasing others that will join the show, including Firefly's Jewel Staite, who takes on the role of Rachel Turner, a tech genius and roboticist who lives in a future almost fully controlled by technology.

"A descendant of a long line of inventors — one of whom turns out to be someone from the DC Universe!" writes TV Line about the character. "Rachel believes that her creations can make that world a better place. Alas, what the brilliant beauty cannot foresee is that her work is destined to fall into the hands of immortal baddie Vandal Savage, who will use it to take over the world. Unless Rachel can team up with the Legends to stop him."

The majority of fan theories speculate that Rachel is probably a descendant of none other than The Atom himself, Ray Palmer.

Sara gets a new love interest

Although Sara's previous romantic entanglements involved Oliver Queen and Nyssa Al Ghul, now that she's died and come back from the dead, she's probably a little unsure about making a romantic connection with anyone. However, she will meet someone on Legends that just might change her mind about falling in love again.

Enter Lindsay Carlisle: Sara meets Lindsay in the 1950s while traveling through time.

"At the start of this episode, we find Sara Lance completely out of place, both in time and place, visiting 1958 'Pleasantville, America' — and also out of place emotionally," said executive producer Phil Klemmer to Entertainment Weekly. "After Sara was brought back from the dead on Arrow, she hasn't been herself — she's been consumed by a quest for bloodshed and incapable of having romantic feelings for anyone. The strict social norms of the '50s makes this the last place Sara Lance would ever expect to find love with a young, closeted nurse, but that's how love works — it finds you."

Big budget special effects

Although the special effects of both The Flash and Arrow are impressive, expect even bigger and better from Legends of Tomorrow. Promos and trailers released by The CW show a lot of science fiction elements, a lot of explosions and a lot of action, more than probably any other series the network has ever aired.

This is, in part, is due to the short season of Legends of Tomorrow. It's airing as a limited event, with only 15 episodes.

"And the reason they are doing a smaller amount is because they want to take the same amount of money that they would for 23 episodes and put it into 15 so that they can really make it big," said Caity Lotz last year at the Superman Celebration. "The new show is going to have a lot of special effects, kind of like those on The Flash, and also a lot of the fighting and stunt stuff that you see on Arrow. So I think it's really going to be an interesting combination. Who knows what's going to happen for season two."

Legends of Tomorrow premieres on The CW on Jan. 21.