When Arrow Season 6 picks up, "everything has changed," at least according to the latest promo for The CW's flagship DCTV show. The ominous teaser is jam-packed full of action and cameos, from Manu Bennett's Deathstroke to the sinister Black Siren.

"You and I walk between two worlds," Deathstroke tells Oliver in the TV spot. "We can only do that for so long."

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The promo briefly flashes back to the Season 5 finale, where Oliver watched on helplessly as Lian Yu blew up with his friends on it. His son William's voice can be heard over the explosive scene, saying, "The Bad Man is here." When Oliver asks William where the Bad Man is, William points over Oliver's shoulder, and the teaser cuts to an action-packed montage.

In the montage, Oliver fires off arrows and leaps off a building. It also provides a blink-and-you'll-miss-it look at Black Siren, the evil Earth-2 doppelganger of Laurel Lance, as she blows up the Star City Police Department. Another scene shows the door being blown off the bunker's elevator.

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At the end of the Season 5 finale, the series teased multiple — and major — casualties after Prometheus blew up the island while Felicity, Dig, Thea, Curtis, Renee, Dinah, Slade “Deathstroke” Wilson, Nyssa al Ghul and William’s mother Samantha Clayton were still on it. Midway through the episode, Felicity discovered with horror that the whole island was rigged with hundreds of explosives; what’s worse, these explosives were connected to Adrian Chase himself. So long as Chase was alive, the bombs wouldn’t go off; however, if he was killed, all of the bombs would detonate. So, at the end of the episode, he shot himself in the head to teach Oliver a lesson and triggered all the bombs on the island. Oliver and William watched in horror as the whole island went up in flames, and the episode drew to a close.

Starring Stephen Amell as the Emerald Archer, Arrow returns Thursday, October 12 at 9pm ET/PT on The CW. The series also stars Emily Bett Rickards, David Ramsey, Willa Holland and more.