Onyx is a young African American girl with an athletic built and medium-height. She has brown eyes and black hair arranged in dreadlocks. She wears one helix piercing on her ears. As part of her Shadows uniform, she dons a purple bandanna on her forehead and a matching turtleneck, which she can pull up to cover her mouth, leaving only her eyes exposed and taking the shape of a ninja mask.
Onyx was raised by her maternal grandfather, Will Everett aka the Amazing Man, whom she called Poppa Willie. Though he was kind and treated her well, she grew frustrated by his limited "Booker T." philosophy and wanted more. She was recruited into the League of Shadows at age 11 by Sensei himself, promising to train her to be the best version of herself. She enjoyed being on Infinity Island and came to see the Shadows as family. Her grandfather died a few years after she left, she had never seen him again.
Onyx followed Artemis from her house to the college library. As she covertly approached her from behind, Arsenal and Arrowette engaged her in combat. She fought fiercely, but was ultimately knocked out.
When she came to, she assured that she didn't mean to harm anyone and had mistaken Arsenal and Arrowette for League of Shadows agents. She claimed to having defected from the Shadows specifically to warn Artemis that Cassandra Savage was going to attempt to infiltrate the Team, professing defection from the Shadows. In that precise moment, Cassandra stepped out of the shadows and said just that. Onyx insisted that she was lying and that she had overheard her plotting with Lady Shiva. Not believing either one of them, Tigress decided to sequester the two until they could sort out the truth.
En route to the Vault, the convoy was attacked by League of Shadows gunning for Cassandra. Onyx escaped from her cuffs and took out the last remaining Shadow. Later she admitted that she could have freed herself and escape anytime she wanted.
At the Vault, Onyx posited that the attack was staged so as to lend credence to Cassandra's story.
Onyx allowed Looker to read her mind to confirm her sincerity. However, because Shadows are trained to thwart psychic readings, Tigress enlisted Cheshire to interrogate Onyx, hoping to see through Shadows' counter interrogation techniques. Onyx was in awe of Cheshire, "the one who got away" and inspired her to escape the Shadows too. She told Cheshire her backstory and despite having enjoyed being with the League of Shadows, things took a turn for the worse when they moved to Santa Prisca and Ra's al Ghul and Sensei were replaced by Deathstroke and Lady Shiva. At that point, she realized she was nothing more than a weapon for them. Cheshire didn't believe her, because she recognized counter interrogation tricks in her responses. Onyx claimed she couldn't avoid conditioning her responses, as she had been trained to do so since she was eleven, but she assured that she wanted to help and to be a normal human being again.
Moments later, Black Spider and Rictus infiltrated the compound and Tigress released Onyx to help her protect Cassandra. Despite initially protesting, Onyx followed suit and attacked Rictus. The ensuing brawl came to a halt when Lady Shiva appeared and held Orphan hostage. Before slinking away, she demanded Cassandra Savage to be delivered to Santa Prisca in 24 hours. Certain that this had to be a set up, Onyx volunteered to go along to Santa Prisca and watch Tigress's back.
Aboard the Super-Cycle, Onyx, Tigress and Cassandra traveled to Santa Prisca. Cassandra broke the silence, regretting the present predicament and insisted again that Tigress traded her for Orphan as soon as they reached Santa Prisca. Onyx accused her of making that proposition knowing fully well that Artemis would reject it, as she did. The two bickered until Tigress proclaimed they had to work together in order to save Orphan. Onyx and Cassandra begrudgingly agreed.
Nearby Santa Prisca's bay, Onyx and the others dove underwater, with Cassandra pointing the way. Onyx was saved from a shark attack by Cassandra and after reaching the shore, she returned the favor and saved Cassandra from falling off a cliff. At top, they neutralized the Shadows standing guard and then converged. Onyx pointed out that they were on the wrong the side of the island and the sun would rise before they reached their destination, so Tigress decided to find a hiding place and wait the day out.
After sunset, they set off into the jungle again and finally reach the Shadows' HQ. Onyx was flummoxed by how Tigress managed to turn off the security alarms and then they all sneaked inside the compound. They ran stealthily through the corridors, knocking out every guard in the way, until Cassandra posited that Orphan might be in cell block A. Without hesitation, Onyx grabbed her from behind, pressing her blade against Cassandra's neck. She insisted to Tigress that Cassandra was a mole and could not allow her to go any farther. Suddenly, Cassandra flipped Onyx over her head and removed her Glamour Charm, revealing her scar and amputated arm to be just an illusion. Onyx boasted to Tigress that she was telling the truth all along, but much to her chagrin, Tigress pointed out that she could still be a mole. Onyx and Tigress were ready to fight Cassandra, but they became outnumbers when Black Spider, Rictus and Shade showed up. Luckily, Cheshire came out of nowhere and provided a smokescreen, allowing them to escape. They reached Orphan's jail cell, but their pursuers caught up with them.
Tigress played for time, and as the Shadows discussed their plan, it became clear that they had used Onyx as a distraction, having come to doubt her loyalties to the Shadows under the new management. Once Orphan freed herself, she cut the lights and the two sides fought. Onyx and Savage battled, with Onyx coming out on top. However, the lights were soon restored and Tigress, now wounded, and her time once again found themselves hopelessly outmatched. Unexpectedly, Shade teleported the group away to the beach.
Shiva was able to follow them. Onyx and Orphan helped Tigress to the Super-Cycle and dressed her wound. Shiva provoked Orphan into a battle, but Orphan opted not to kill her and Tigress's group left Santa Prisca.
When they caught up with Cheshire, she was making a seemingly suicide assault on Sensei and a Red Hooded Ninja. Onyx listened closely as Tigress and Cheshire talked about the trauma Cheshire had suffered and her fears of bring her family into her cage. Onyx related, knowing that she too had once fled a self-made cage, running away from her grandfather to join the Shadows. Sensei confessed that the Shadows had sought to manipulate both of them to make them better weapons. Since they were no longer in the business of Shadows, Sensei offered to help both Cheshire and Onyx process their experiences as Shadows, an offer backed up by Ra's al Ghul. Cheshire and Onyx both opted to stay and accept their help.
Later, Onyx sat in meditation with Sensei, Cheshire and the Red Hooded Ninja.
Sword: Onyx carries a katana sheathed on her back.
Whip: She wields a retractable whip with a double-prong hook at the tip.
Onyx Adams is a vigilante in Gotham City and a former member of the League of Assassins.
This is her second animated appearance; she first appeared in the animated movie Batman: Bad Blood.
Jerome Moore, co-creator of Onyx, designed her look for season four. When adapting her for the show, it was felt that her original design from the 80s needed updating, with Greg Weisman declaring "No capes!". Her update included adding light armor and pouches to keep her in line with the show's usual aesthetic for "street-level" characters. Her comic design had a black and white palette inspired by the onyx gemstone, but Moore decided to replace the white with purple to create more visual interest while steering clear of color schemes strongly associated with other characters.
Moore had hoped the voice actor chosen would reflect his vision for the character, "an educated young woman, more refined than "street."" He worried about her getting a "stereotypical... sassy" voice, but was pleased with the choice of Logan Browning, who he got to meet at a recording session.