The Black Flash will officially be a part of DC's "Legends of Tomorrow" Season 2. Also, the official plot description and promo clip for episode 10 'The Legion of Doom' is provided here.

According to Entertainment Weekly, The Black Flash will officially return in DC's "Legends of Tomorrow" Season 2. In a recent interview during Sirius XM Radio Show, showrunner Marc Guggenheim revealed,

"We are going to be seeing the Black Flash on Legends. Teddy Sears portrayed the Black Flash in "The Flash" Season 2 finale. Until now, it's still undecided whether or not the actor is going to reprise his role in DC's "Legends of Tomorrow" Season 2 as he currently plays a role in FOX's "24: Legacy."

Black Flash made its first appearance in the network's DC TV universe in the Season 2 finale. Hunter Zolomon (Teddy Sears), a.k.a. Zoom transformed into Black Flash by Time Wraiths after Barry Allen (Grant Gustin) defeated him.

Black Flash serves as the Grim Reaper for speedsters in the comics. When speedsters die, Black Flash brings them back to life using the Speed Force. 

As for the official plot synopsis of episode 10, Spoilers Guide notes, "The Legends are currently in the quest to search for Rip Hunter (Arthur Darvill), but first must focus on locating the Spear of Destiny. Dr. Martin Stein (Victor Garber) thinks he has the perfect person to help but knows that being involved with such mission will be risky.

Meanwhile, Malcolm Merlyn (guest star John Barrowman) and Damien Darhk (guest star Neal McDonough) realize that Eobard Thawne (guest star Matt Letscher) is setting them with conflict against each other."

DC's "Legends of Tomorrow" Season 2 episode 10 is titled as "The Legion of Doom". The upcoming episode is scheduled to premiere on Tuesday, January 31, 2017, at 9:00 p.m. EST first and exclusive on The CW.