Topaz (Steven Universe)

Topaz is an antagonist in Steven Universe.

Topaz is a Homeworld Gem fusion who serves under Yellow Diamond. She, along with her partner Aquamarine, serve as the main antagonists of the final four episodes of the fourth Season and will return as antagonists in the fifth Season.

Past
At an unknown point (likely after the Crystal Gems defeated Holly Blue Agate and broke Greg Universe out of the Human Zoo) she and a Aquamarine were personally assigned by Blue and Yellow Diamond to find and retrieve several specific humans.

Season 4
In "Doug Out", Topaz and Aquamarine are briefly seen at the end of the episode approaching Onion.

In "The Good Lars", Topaz and Aquamarine are yet again seen at the end of the episode, this time approaching Sadie.

In "Are You My Dad", after Steven realizes that Onion, Lars, Sadie and Jamie have all gone missing. After splitting up, Steven and Connie manage to find Aquamarine in the woods. As soon as Connie states her name, Aquamarine happily flies around and tells Topaz that she "found a Connie", revealing that Topaz has trapped all of the missing people inside of her body. Topaz soon reveals that she is actually a Gen Fusion, unfusing and refusing herself over Connie in order to trap her, and when Steven tries to attack, Aquamarine takes out her Wand, forms a bubble around Steven and slams him into a tree, knocking him out. As she and Aquamarine walk off, Aquamarine casually states that their job is so easy, Topaz really could've done it all by herself. But she just remains silent.

In "I Am My Mom", Steven tells the Crystal Gems about Topaz and Aquamarine, terrifying Pearl, who realizes that they were personally sent by Blue and Yellow Diamond to get humans for the human zoo. To make matters worse, Garnet and Amethyst realize that, should Topaz and Aquamarine reach their ship, Steven's friends will be gone forever since Navy stole their ship. Upon getting a picture showing Funland from Connie, Steven and the Gems head there and confront Topaz and Aquamarine. The Gems try to get Topaz and Aquamarine to release Steven's friends, however, they refuse, revealing that Steven's friends are being captured because they were all on a list created by Peridot 5XG after Steven told her about his friends when she was still aligned with Homeworld, also unintentionally revealing that "My Dad" is actually Steven's father Greg, as he referred to him by that at the time.

The Gems then try to fight Topaz and Aquamarine, however, they find themselves unable to do so without endangering the lives of the humans, with Aquamarine using this to her advantage, stating that Blue Diamond never said to bring the Humans back alive, nearly having Topaz crush Jaime's skull. Steven then tells Aquamarine that he is "My Dad", Topaz then captures him in her body and walks back to the ship. Aquamarine then starts to pilot the ship and prepares to fly back to the Zoo, however, Steven manages to use his Bubble Shield to blow apart Topaz and free everyone. Topaz tries to fight them off, then grabs sadie. Lars tries to help but is soon paralyzed with fear, leaving Sadie to rescue her self. Just as Alexandrite manages to catch the ship and everyone (sans Lars) tries to jump to safety, Aquamarine uses her wand to freeze everyone in place. Knowing the that he has no other option, Steven reveals himself as the Gem who started the rebellion and shattered Pink Diamond, Rose Quartz, causing Topaz and Aquamarine to abandon their original mission and capture Steven instead, flying off to the Gem Homeworld with him.