The fourth season of "Arrow" (which premieres October 7 on The CW) is all about resurrection as Oliver Queen (Stephen Amell) reinvents his superhero persona, Thea (Willa Holland) deals with the after-effects of The Lazarus Pit, and a character from a canceled TV show is back to help in resurrecting someone else.

Here are six things you need to know about the new season of "Arrow."

1. Arrow Is Dead! Long Live the New Arrow!

Everyone thinks Arrow was Roy (Colton Haynes) and Oliver Queen is not about to resurrect his alter ego. As Amell told TV Line. "Roy outed himself as the Arrow, so if I were to recreate the suit and go out, it would undo all of the sacrifice that he made. So the Arrow persona, for better or for worse, it can't exist anymore." However, Queen (as Green Arrow?) is back with a bitchin' new outfit because he's still got a city to save. He also has a spiffy new lair to accommodate the growing Team Arrow, per EW.

2. There's a New Bad Guy in Town

Neal McDonough ("Public Morals," "Justified") is playing Damien Darhk,who producers tell TV Line, is "a mysterious and sophisticated villain, and an adversary of the late Ra's Al Ghul. Now the leader of his own clandestine group, this cunning foe will prove to be one of the Arrow's greatest challenges." As executive producer Marc Guggenheim told EW, "He's really pure evil, and he will stop at nothing to achieve his ends." What are his powers? Guggenheim, won't say exactly, telling TVLine, "He can definitely kick your ass, but he can do it in a different way than Arrow's other foes.

3. Constantine, Back From the Dead!

Matt Ryan will reprise his role as the trench-coated, chain-smoking exorcist from NBC's short-lived "Constantine" for one episode, CW announced at the Television Critics Association in August. He'll appear in the fifth episode of the show's fourth season, titled "Haunted," in which he provides critical "critical support to Oliver when arrows aren't enough," EW reports.

4. Olicity 4Eva!

Now that Felicity (Emily Bett Rickards) and Oliver have finally gotten together, you'll be seeing a lot happier, relaxed Oliver. Says Guggenheim to EW, "Oliver's got a new outlook on life...We played him as a guy who was returning home from war with PTSD for the first three years. Now he's put those demons to rest, or so he thinks, and there's a lightness to him as a result of all the things he learned last year."

5. Diggle and Arrow Make Up

"Their reconciliation, how they get there, is going to be a bumpy ride. It's not going to be fully resolved," executive producer Wendy Mericle tells TVLine. Diggle (David Ramsay) also gets a new crime-fighting look. Not everyone was digging Digs' new helmet though, with fans thinking it looked too much like Magneto. "I know there's a lot of criticism that it looks like the Magneto helmet. But by the time you see Diggle in action –- we also get into what the helmet can do -– you won't be thinking of the X-Men at all," he told TV Guide.

6. Thea Is Now the Troubled Superhero

With Oliver temporarily out of the picture, his little sister has donned a hood and mask of her own as arrow-slinging avenger Speedy. Amell tweeted that the reaction to the premiere will be "What's wrong Speedy?" since Thea's not the same person after dying and being brought back to life.

What's wrong Speedy?

— Stephen Amell (@amellywood) June 18, 2015