With the announcement that Battlestar Galactica alum Katie Sackoff was going to be playing Amunet Black aka Blacksmith, figured it was a good time to do a quick comic book history of the character. She was created by Geoff Johns and Ethan Van Sciver, first appearing in Flash: Iron Heights. Here you can see Blacksmith leading the rogues in a very comic book looking outfit.
Amunet Black, or Blacksmith, has been the head of The Network, an underground black market for weapons and contraband, based in Central City and Keystone City for over fifteen years. Black was also briefly married to the villain Goldface, but when they separated, she stole the elixir that granted him powers and modified it to allow here the ability to merge metal and flesh, shaping it to her will. It was very important to her that the Network remain a secret. If anyone was close to giving up the Network, she would either erase their memories of it or, in the case of Goldface and Hunter Zolomon almost finding it, she would send a rogue like the Trickster to stop them.
She had a desire to take over the twin cities using the rogues, or at least a new group that included the Weather Wizard, Mirror Master, Magenta, Murmur, Girder, Plunder and Trickster with Blacksmith in charge. She worked with her rogues to help them improve their powers and work as a team. Then, before going after the Scarlet Speedster, she took out his allies… framing Pied Piper for murder, took out Chunk, trapped Cyborg and officer Fred Chyre in the mirror universe and along with all the Keystone City police. Then caused financial problems for Jesse Quick and had Jay Garrick's wife end up in a hospital in Denver, putting him out of the way. They then created a barrier preventing anyone from entering or leaving the cities.
With all that in place, Blacksmith had the rogues attack the Flash hard and fast, leaving him exhausted and injured, a move that would likely to have succeeded if the Thinker didn't interfere, wanting the Flash for his own purposes. They went after the Thinker, defeating him and going back after the Flash who they trounced. Goldface, who was trying to help the Flash, escaped and rallied the citizens of the twin cities to rise up against the Network / Rogues, giving the Flash the opportunity to defeat Weather Wizard, Mirror Master, and Trickster. Blacksmith, who had turned her body into ebony metal, tried to collapse the bridge connecting the two cities, but the Flash was able to rebuild it and defeat her by sending her out into the river on a barge, disconnecting her from her network. She ended up in Iron Heights.
It makes sense to bring this character in this season with the face the Thinker is the big bad for season four. Sackoff makes the second BSG alum to become one of the Flash's rogues. Aaron Douglas appeared in season 2 as the Turtle, an rogue with the ability to slow down time.