Derek James, aka Sideways, is the only character in DC’s New Age of Heroes that is wholly new. There has not been a Sideways before this title, and until Sideways #1, we had not been introduced to Derek. And yet, unlike our initial two entries, this powered individual’s connection to Metal is much more pronounced and obvious.
Derek and his mother were visiting Gotham when Challengers Mountain appeared in the center of the city. In Sideways #1, we see him fall into a crevice created by the arrival of the mountain. Derek explains later in the issue, “I think I went into whatever energy the mountain was putting off.” We know that he actually fell through a rifts into the Dark Multiverse, where he gained the power to teleport and immediately used his new ability to get back to Gotham. While it seems like his teleportation capability came from his time in the Dark Multiverse, it's more likely he has cosmic metal in his make-up and his time there just sparked his latent powers.
The Terrifics are a new team consisting of Mr. Terrific, Plastic Man, Metamorpho and a new Phantom Girl. It's shown in Dark Days: The Forge #1 that Mr. Terrific is working with Batman on the Dark Multiverse mystery, and that he knows about the Dark Knight stopping Plastic Man (in a dormant, egg-shaped state) in the Bat Cave. We learn in the pages of Metal that Plas' unstable cells make him a super-conductor for vibrational energy, and he went into his dormant state when he took on too much dark energy. Mr. Terrific has since been hauling the Plas egg around for most of Metal.
The Terrifics #1 just hit stands, and in it we learn that after the events of Metal, Simon Stagg has acquired Mr. Terrific aka Michael Holt’s company, TerrificTech. Holt goes to see Stagg when his T-Sphere’s alert him that the industrialist is accessing dangerous, experimental equipment. He arrives to find a portal open to the Dark Multiverse, and Metamorpho being held in front of it. Terrific brings out the Plastic Man egg in hopes the hero may be able to close the gate. Instead, Terrific, Plastic Man, and Metamorpho are all pulled into the Dark Multiverse. Very shortly after they arrive they meet Linnya Wazzo aka Phantom Girl and discover a distress message from none other than Alan Moore and Chris Sprouse's Tom Strong.