A shapeshifting entity known as Gyaos Vader lived in an abandoned temple on Kessel at the time of the Galactic Civil War. Its true form was that of a flying, bony creature with reptavian traits. This mysterious being could metamorphose into the Sith Lord Darth Vader. Gyaos Vader was killed in its Kesselian lair by Luke Skywalker, a hero of the Rebel Alliance, some time prior to the Battle of Yavin.
In the early years of the Galactic Civil War, a changeling named Gyaos Vader lived in an ancient temple on Kessel, a barren planet located in the Outer Rim Territories. In its natural form, this being looked like a skeletal bird, but it could take the likeness of Darth Vader, Dark Lord of the Sith and second-in-command of the Galactic Emperor Palpatine.
Around 0 BBY, Gyaos Vader captured the Jedi Master Obi-Wan Kenobi and held him prisoner on Kessel, the asteroid-shaped planet. The young Tatooinian Luke Skywalker, who had began his Jedi training under Kenobi, came to the rescue of his Master. Once Skywalker reached the creature's lair in the temple, he faced Gyaos Vader, who had taken the shape of the Lord Vader in order to surprise him. Both opponents drew their lightsabers and engaged in a duel. During the fight, the creature turned back to its true shape and began flying around the room. Skywalker and the changeling traded several blows, but the young Jedi got the upper hand. Having killed Gayos Vader, Luke Skywalker freed Master Kenobi and set off for Iskalon, where the golden droid C-3PO had been been taken hostage by another shapeshifter.
Gyaos Vader in the 1987 Star Wars game.
Gyaos Vader was one of the stage bosses in the Japanese Star Wars 1987 video game. The game featured various fake Vaders which were all revealed to be shapeshifting monsters. The canonicity of this game and the creatures it features is dubious. The room Gyaos Vader was fought in featured a golden mask similar to that of the Egyptian pharaoh Tutankhamun.
According to both "Game On!," an article published in Star Wars Insider 135, and the game manual, the fake Vaders (Clados, Gyaos, Sasori and Wampa) were "intended as illusions representing Luke's fears, like the Cave of Evil scene in Empire Strikes Back." However, since those game opponents were able to kidnap Luke Skywalker's allies and hold them prisoner, this article assumes they were real creatures rather than illusions. Additionally, the Vader-shaped figure that Skywalker fought in the Cave of Evil was more than mere illusion, being in fact a protean dark side entity known as the Dark Spirit.
In the original game manual in Japanese, the character was called Gyaosu Beidā (ギャオスベイダー). While Beidā is a transliteration of "Vader" in Japanese, Gyaosu and Gyaos refer to a number of giant, pterosaur-like monsters appearing in the Gamera film series from the Daiei Motion Picture Company.