Sugilite

Sugilite is the main antagonist of Steven Universe episode Coach Steven. She is created when Garnet and Amethyst dance to synchronize and fuse together. She is voiced by Nicki Minaj.

Appearance
Sugilite is humongous; at least two times as tall as the fusion gem Opal. Her skin color is a slightly darker purple than Amethyst's and she wears a ripped, dark purple and black with burgundy costume similar to Garnet's body suit. She possesses four arms like Opal and wears a visor to cover her lower four eyes while her fifth eye is located above her brow. She possesses a giant plume of spiky, dark violet hair. Her eyes tinge red when she's angry. She has a gem on her chest and two sugilite gemstones on each hand on her lower pair of arms.

Personality
Sugilite combines Garnet's headstrong, unwavering nature with Amethyst's recklessness and immense free will. Even when first fused, Sugilite thinks of herself not as a fusion between two personalities, but as a single, complete individual. The mere assertion that she should separate has caused Sugilite to go into a fury.

Sugilite cares for herself, first and foremost. Though she will carry out mission objectives, she will not do anything that she does not want to do, and will not hesitate to use force to get what she wants. This has caused at least one dangerous situation, wherein Sugilite, enraged that she was left behind during a mission and asked to split up, nearly killed Pearl.

Trivia

 * In gemstone mythos, sugilite stones are known to be gems that balance the mind and soul and serves as protection from anger and negative feelings; which is ironic given Sugilite's dangerous and unstable nature (in other words the opposite).
 * She has Amethyst's negative attitude towards Pearl and her desire to do whatever she pleases, and Garnet's Body shape and Glasses.
 * Like Steven, her gemstone is not a birthstone.
 * Sugilite bears a striking resemblance to Roy Koopa from the Super Mario Bros. Series.
 * Sugilite could also be based on an Oni, a Japanese demon or ogre, due to the gem being first discovered in Japan by Professor Ken-ichi Sugi.
 * She also strongly resembles the Hindu goddess Kali. Kali is often portrayed as having four arms and a very destructive nature. Sugilite's long and somewhat wild-looking dark hair resembles common portrayals of Kali as well. While Kali is usually described as violent, she's still often seen as a destroyer of evil and some legends even show her to have a caring, maternal side.
 * Sugilite shows in the episode "Coach Steven" that if multiple gems are fused for too long, they can slowly lose their individuality.
 * Sugilite also seems to have sugilite gemstones as fingernails faceted in different shapes. The index is shaped as a star while the rest appear to be square.
 * Sugilite is the largest character to be revealed in the show so far, about two times taller than Opal.
 * Sugilite is the only known Crystal Gem with three gemstones.
 * She was defeated by her own weapon thanks to Pearl's strategy planning.
 * She is the only fusion Gem who's full transformation was seen on screen while Opal's transformation was interrupted and not seen.
 * Sugilite, Amethyst, and Opal are the only Gems who haven't been seen bubbling away gemstones.