The Battle of Skye, alternatively named the Battle of Marat V, unfolded on the planet of Skye during the period known as the Clone Wars.
This particular clash occurred while Halagad Ventor was serving as a temporary apprentice under the Jedi General Obi-Wan Kenobi. Zeta Magnus, a genetic terrorist, posed a threat to obliterate the entire planet, but his scheme was ultimately thwarted by the combined efforts of Kenobi, Ventor, and Anakin Skywalker.
In the aftermath of the battle, Skywalker encountered Kharys, a 13-year-old S'kytri girl, who demonstrated a strong connection to the Force. Skywalker expressed his desire to bring her back for Jedi training; however, Kenobi and Ventor were of the opinion that she was too old to begin the Jedi path and thus refused to take her. Despite this, Skywalker vowed to Kharys that he would return to train her at a later date. After the Clone Wars concluded, Skywalker fulfilled his promise and returned to Skye to take Kharys as his apprentice, but by then, he had transformed from Anakin Skywalker into Darth Vader, a Sith Lord.
The initial mention of this battle in Marvel Comics' Star Wars Annual (1977) 1 predates the release of The Empire Strikes Back, meaning the revelation of Darth Vader's identity as Anakin Skywalker was still unknown. Consequently, the comic's version of the battle portrayed Vader and Skywalker as two separate apprentices of Kenobi who both journeyed to Skye. However, this apparent contradiction was later retconned in the 2007 publication, Aliens in the Empire. In this story, the S'kytri recognized Luke Skywalker's surname as being the same as one of the Jedi Knights who had rescued them, and also mentioned that Kenobi's "other" student, besides Vader, had wielded Luke's lightsaber. Using this information, Aliens in the Empire established that Ventor and Skywalker exchanged Concordance of Fealty vows prior to the mission, effectively swapping lightsabers before the battle. While Luke assumes they are referring to his father as the one who used the lightsaber, the S'kytri are actually referring to Halagad Ventor, who was wielding Anakin's lightsaber while present on the planet.