Nichrome is a four-legged creature, not recognizable by Equus, Earth, or Homeworld standards. His skin is described as black as tar, and his head resembling that of a sock puppet with eyes as white as stars.
Nichrome is a sadistic, and manipulative alien, claiming to enjoy "breaking" people over simply killing them. This trait is shown on numerous occasions, mostly towards the prisoners of Tambalon, or to anyone he knows he has power over, including his own soldiers and comrades. This sort of manipulation though is mostly for his own personal satisfaction, him even willing to lie to Grogar about the "deaths" of the Harmony Gems in order to gain his favor. He also has been known to gain favors from multiple people so they can work for him.
His logic towards Gem society seems to be a bit different from what many others believe, most notably the idea that Pearls are a much higher ranking Gem than other Gem types, even referring to Pearl as the leader of her group on first seeing her. This is extended further when he asked Yellow Pearl and Blue Pearl to order their own Diamonds to get away from him.
Little is known about his backstory, though as he was following under Grogar, it can be assumed he was one of the Aliens under The Diamond Authority's containment before Grogar released him.
During a night patrol, his group managed to locate Flint, Pearl, Peridot, and Emerald within Homeworld's outskirts, reciting the end of a story Pearl was telling about Red Diamond. He compliments her about her story skills, referring to Pearl as the leader of the group, before he and his group took them back to Diamond City, which at the time was known as Tambalon. He brought the four right to Commander Cerrosafe, before heading off to the council to watch them being marked. He appears later after the four manage to escape, staying by Connie Maheswaran's cell. Blaming her in part to Cerrosafe's death, he then tells her to stop trying, as Steven Universe had been killed by Grogar, and as such she had no reason to leave.
Nichrome plays a prominent role again within Moles in the Burrow, and the Season 8 finale: when he asked Twilight Sparkle to come in, insisting that she should become his spy to better secure the safety of her family and friends. When she refused though, he attacked her and stated he will "make her scream for Celestia", only to be stopped by Tempest Shadow, who in turn warns him he'll face her if he tries that again. Determined to win her over, Nichrome ventured into Canterlot, and tried poisoning Fulgurite, Pinkie Pie, and Steven Universe. Afterwards, he returned to Tambalon and reported the job to Grogar, but was forced to go back out to make sure it actually did the job, finding Grogar wanted to kill them himself. He arrives back on scene, but when he saw Steven recovering, he stormed out in anger and demanded him to die already, exposing himself and his plan to everyone.
He was released, but upon returning he told Grogar that they all were dead to keep his good favor, yet still got everyone on security for threats outside of Tambalon. Sometime later before the wedding, Nichrome finds Twilight and asks once more about her decision to become his spy, only to reveal that he never needed her and just wanted to watch her break before sending her to be executed. He joins them for the execution, him assigning Flint to do so. He tries to force Flint to continue, but gets brutally beaten up for it.
My Little Universe II
In the final season, his most prominent involvement was in the rescue of Grogar. He tries fighting off the Harmony Gems during that invasion, but he cowers away and runs off for his life along with the rest of his troops. It is revealed by Olson that afterwards, he got severely punished and assumedly killed by Grogar for his cowardice.