Andrew Kreisberg, the writer/producer who is in charge of shepherding the Arrow spinoff Flash into existence at The CW, told Spoiler TV that even though Barry Allen will now be getting his own standalone pilot, that doesn't mean fans shouldn't expect what's happening in Central City to impact the world of Arrow.
“What happened in Central City at the end of [the fall finale] was certainly big news,” as the S.T.A.R. Labs particle accelerator failed, resulting in the origin of The Flash, Kreisberg told TVLine. Confirming that Barry's third appearance on Arrow--which would have been as The Flash--has been "scrapped," the story quoted the EP as saying, “Right now, we’re focusing hard on writing the Flash pilot and breaking the rest of the season of Arrow. But hopefully there will be some synchronicity between the two [shows], in anticipation of getting to see more of Grant [Gustin] and The Flash.”
Of course, there's plenty more for Oliver to deal with, as Deathstroke the Terminator was revealed as the man who's been pulling Brother Blood's strings--a game-changing revelation, considering that Oliver has repeatedly intimated that he killed Slade on the island before returning to Starling City. What's not immediately clear is the connection between Deathstroke and the League of Assassins, who spent the first half of the seasons sending emissaries to Starling, looking for Sara Lance (and who are now doubly incentivized to come back again, since Moira sold out Malcolm Merlyn to Ra's al Ghul).
Nyssa Raatko, the daughter of Ra's al Ghul, will appear in the season's upcoming thirteenth episode, titled "Heir to the Demon," looking again for Sara. Played by Katrina Law, who was apparently up for the role of Shado, that bit of trivia might actually inform some of the relationship between the Deathstoke story and the League of Assassins story in the back half of the season; TV Guide claims she didn't get the job, at least in part, because the connection between Law and Manu Bennett, who plays Slade Wilson and appeared with Law on Spartacus, may have been a bit too much. Now that she's on the show, does that suggest her character won't share much screen time with Deathstroke? And if so, does it indicate that those are--at least for now--very different storylines?
Of Nyssa herself, Kreisberg told TV Guide, "She's the next wave of the League of Assassins that comes to Starling City. She's certainly exotic, beautiful and smart. She has some interesting secrets as well."
As to the nature of those secrets? Remember that Sara Lance has been referred to as "The Beloved." Given the relationship between Batman and Nyssa's sister Talia, it's easy enough to wonder whether Black Canary will turn out to have been in a relationship, either with Nyssa herself or with her extremely dangerous father.