First Appearance Queen Trios

Both Star Wars Annual #1 and Darth Vader Annual #1 were published in December 2015 and introduce new characters that would appear in the ongoing titles following the Vader Down story arc.  Eneb Ray, introduced in Star Wars Annual #1, is the main antagonist in the Rebel Jail story told in Star Wars #16 - 19.  Darth Vader Annual #1 has the first appearance of Queen Trios, who next appears in The Shu-Torun War story arc in Darth Vader #16 - 19.  Unlike Eneb Ray, who has yet to reappear in a Star Wars title, Queen Trios is seen again in The Ashes of Jedha arc in Star Wars #38 - 43.

Queen Trios is first introduced as Princess Trios, the youngest child of the King of Shu-Torun, in Darth Vader Annual #1.  Shu-Torun is an ore-rich world whose mining production is important to the Empire.  Darth Vader travels to the planet to ensure the Empire's increased quota is fulfilled.  Vader is met on the landing platform by Princess Trios.  Vader is carrying a gift which he intends to give to the King himself and Trios leads him to a celebration ball arranged by the King.  At the celebration, Vader is attacked by assassins and demands Trios takes him to her father.  Vader knows the assassins were sent by the King.  Meanwhile 0-0-0 and BT-1, who traveled to the planet with Vader, are also on their way to the King's throne room.  Trios leads Vader into a trap meant to kill them both, but Vader escapes carrying the now unconscious Princess Trios.  Outside the throne room, Vader wakes Trios who sees that Vader has killed the guards.  She raises a pistol to shoot Vader in the back, but he cuts off her hand with his lightsaber before she can pull the trigger.  As the pair enter the throne room, we learn that 0-0-0 and BT-1 has killed the King, his two older children, and additional guards.  Vader then gives the gift to a distraught Trios as Vader explains it is "a small reminder of what happens to worlds who resist the Emperor."  It is a rock from Alderaan.  Vader then crowns Trios, declaring her the ruler of Shu-Torun.

Star Wars: Darth Vader Annual #1a - Marvel Comics, U.S. (December 2015)
1st appearance of Queen Trios

Star Wars: Darth Vader Annual #1b - Marvel Comics, U.S. (December 2015)
1st appearance of Queen Trios

In The Shu-Torun War story arc, Queen Trios has embraced her role as ruler of Shu-Torun.  She enlists the aid of the Empire, led by Darth Vader, to help quell a rebellion by the ore barons.  In The Ashes of Jedha, Queen Trios is assisting the Empire with mining Kyber from the remains of the planet Jedha.  She employs the Leviathan, a monstrous ship used to excavate ore from planets.  In the final chapter of the story, Star Wars #43, we learn she leaked the plans for the Leviathan to the Rebels and her planet has been stockpiling resources that are not part of the Empire's tithe which she offers to Princess Leia.

Despite her earlier appearances, Queen Trios' first cover appearance is on Star Wars #43.

Star Wars #43a - Marvel Comics, U.S. (February 2018)
1st cover appearance of Queen Trios