WARNING: The following contains spoilers for Wonder Woman #55 from Steve Orlando, Raul Allen, Patricia Martin, Borja Pindado and Saida Temofonte, in stores now.
When it comes to artifacts in the DC Universe, a few storage facilities and heroes pop to mind. There's the Advanced Research Group Uniting Super-Humans (A.R.G.U.S.), which has collected superpowered people as well; the Batcave, where Batman stores items from the Joker, Two-Face and other rogues; the Flash Museum; the Tower of Fate for magical relics; and Superman's Fortress of Solitude, among the many.
We now find out in Wonder Woman #55 Diana of Themyscira has been doing the same, although her collection revolves around one certain item tucked away in a magical realm. As she gifts it to Artemis, her longtime rival who's back on her side, we realize it isn't any ordinary artifact. it's actually one of DC's most dangerous weapons: the Lasso of Submission.
The Lasso of Submission was wielded by the evil Superwoman (Lois Lane) of Earth-3. She came over to the main DC reality in Forever Evil to enslave Earth and used the lasso to wreak havoc alongside Ultraman and his Crime Syndicate. It allows the wielder to force people to obey them and even love them. In other words, it made them submit to whomever owned it, shaping it as something similar to and nearly as powerful as the Anti-Life equation.
The Syndicate eventually failed and Superwoman was imprisoned, only to be brought out to fight the leader of Apokolips in Darkseid War. Things fell apart as her teammates were eliminated, though, leaving the pregnant villain to give birth to Ultraman's child. There was no happy ending, as Grail (Darkseid's daughter) then kidnapped the baby and used it as a vessel to resurrect her father before killing Superwoman. As fate would have it, Wonder Woman, seen as Superwoman's main rival, took the lasso, swearing she would give the weapon to somebody worthy someday. Here, she deems that person to be Artemis, a fellow Amazon.
In the last issue, an enraged Artemis decided to partner with Rustam and oppose Diana, ready to shed blood for the injustice the Quraci army latter doled out to her people, the Amazons of Bana-Mighdall. However, Diana uses her Lasso of Truth to stop Artemis from going down the wrong road yet again, and gets the former Wonder Woman to understand the only path to take in this world is that of peace. Artemis finally comes to her senses and when Rustam, the leader of Amanda Waller's first Suicide Squad, tries to incite war without her, Diana subdues him as well and ends the battle. She crafts a temporary truce, with Artemis helping the Bana-Mighdall tribe accept that war isn't the way forward right now.
Diana finally witnesses Artemis living up to her potential as a leader, and seeing as Rustam somehow destroyed the archer's famed Bow of Ra (the Egyptian Sun God), she gives her younger counterpart the Lasso of Submission, which she has renamed the Golden Promise. Diana no longer has to keep it under her protection, and by bestowing it to Artemis she hopes their rivalry is at an end. The name is quite fitting as it signifies a promise Artemis wants to live up to: To become a better hero.
Artemis has undergone drastic changes recently, not just in losing her bow, but with ties being cut with Jason Todd in Red Hood and the Outlaws. Diana clearly believes in the best in her, despite their numerous run-ins over the years, and is confident she'll wield it the right way.
By giving her the Lasso, it proves to Artemis that the Justice Leaguer considers her a Wonder Woman too and, more importantly, she trusts her. Because this is a weapon, if in the wrong hands, especially that of a lethal assassin like Artemis, it could spell immense trouble and make her one of DC's biggest threats. Thankfully, Artemis has seen the light and is once more a force for good.