The Infinite Frontier initiative has taken DC's canon and given it an interesting remix, bringing back elements and concepts from across the publisher's history. That has included the reemergence of a number of previously-seen characters, whose contexts within the DC universe have begun to change. That was especially in the case in the most recent issue of Catwoman, which brought back a fan-favorite, but forgotten character who hasn't been seen in canon for the better part of a decade. Spoilers for Catwoman #41 from Tini Howard, Nico Leon, Veronica Gandini, and Tom Napolitano below! Only look if you want to know!
The issue saw Selina Kyle's altercation with the various crime families of Gotham evolve into some complicated territory, which happened to have her cross paths with Onyx Adams. While Onyx initially did not trust Catwoman's intentions, the pair agreed to team up together, exchanging their (somewhat flirty) views on romance and inherent goodness.
The pair worked to confront Dario Tomasso, one of the sons of the crime families, and beat up some of the goons of another crime family, the Sullivans. Catwoman and Onyx then part ways towards the end of the issue, but not before Onyx compliments Selina on her current outlook as a vigilante.
Created by Joey Cavileri and Jerome Moore in 1985's Detective Comics #546, Onyx was initially established as a member of the League of Assassins, before deflecting from the team and going to the same monastery as Green Arrow. After teaming up with Green Arrow and Black Canary, Onyx most prominently appeared in the "War Games" storyline, after Batman brought her into the fold to be Orpheus' bodyguard. She would cross paths with the Batfamily a lot over the years, serving as a member of the Birds of Prey in the late 2000s, and training with Cassandra Cain in Bludhaven.
The character was then very briefly reimagined in the New 52 continuity as a member of the Fist Clan in Green Arrow, but has not notably appeared in comics since 2014. She did briefly appear on a Season 6 episode of Arrow, as portrayed by Chastity Dotson.
With Catwoman #41, Onyx gets brought back properly into the DC Comics fold, as well as the larger arsenal of Batman-adjacent characters. Given the way that she and Selina parted ways in the issue's end, it certainly doesn't seem impossible that we might see more of her in the comics sooner than later.
Catwoman #41 is now available wherever comics are sold.