Warning! Spoilers ahead for Star Wars: Crimson Reign #5
In the final chapter of Star Wars: Crimson Reign, Darth Vader confirms the secret history of Darth Maul and his apprentice. While Han Solo's first love Qi'ra abandoned him to become Maul's second in command over Crimson Dawn, it's been revealed that she learned how to do much more beyond leading a crime syndicate. Case in point, Qi'ra and Crimson Dawn have become a major threat to the Sith Lords and their Empire, and it's all thanks to the training and legacy of Darth Maul himself.
Following the War of the Bounty Hunters crossover event which saw Crimson Dawn's resurgence in the galaxy in between Empire Strikes Back and Return of the Jedi, the subsequent Crimson Reign event has seen the crime syndicate becoming a major player with spies and agents embedded all over the galaxy. Executing all sorts of secret schemes to position Crimson Dawn against the Empire, the Dawn's new leader Lady Qi'ra is targeting the Sith specifically, knowing exactly who Palpatine and Darth Vader are and what they're capable of.
With Qi'ra's intimate knowledge of the Sith that few others possess, Emperor Palpatine and Darth Vader speak about the threat of Crimson Dawn in the final issue of Crimson Reign from Charles Soule and Steve Cummings. Combined with her ability to hold her own in a duel with Darth Vader himself thanks to her unique skills in the fighting style Teräs Käsi, Vader and the Emperor have confirmed that she must have received special training. However, Vader also notes that her skills mirror that of Palpatine himself, an indication that the Emperor's former apprentice Darth Maul trained Qi'ra as his own apprentice during the galaxy's dark times.
Clearly, Palpatine and Vader are concerned that Maul taught Qi'ra how to destroy them. As such, Darth Maul's legacy lives on despite his ultimate demise at the hands of Obi-Wan Kenobi in the years just before A New Hope (as seen in Star Wars Rebels). Not only is this the first time Darth Vader is seen speaking the name of a Sith Lord that came before him, but this issue strongly makes the case that Qi'ra was very much Maul's secret apprentice and more than a simple underling. While she may not have abilities in the Force, it's clear that she was trained to fight and take down those that do.
It should also be noted that many of Qi'ra's allies such as the Knights of Ren and the Archivist indicate that she's following a plan created by Maul himself to destroy the Sith. Sending them on missions to recover ancient dark side artifacts and stealing from Darth Vader's fortress, it seems Lady Qi'ra's endgame is imminent with the upcoming Hidden Empire crossover event as she attempts to fulfill one of Darth Maul's greatest wishes to finally get revenge against the Sith who rejected him during the Clone Wars.