―The Bendu explaining the power of uniting the holocrons
A holocron fusion was the merger of a Jedi holocron and a Sith holocron, which could give those who performed it the answers to any questions they asked. It required a darksider and a lightsider to work together, one to open each holocron, so they were rarely performed. Ending the fusion before the holocrons were done could destroy the holocrons used, and cause the two Force users who performed it to get snippets of the information the other was searching for. It was also possible for strong emotions to affect the fusion, causing the answers given to be skewed. By the eve of the Galactic Civil War, knowledge of holocron fusions was rare.
In 2 BBY, the former Sith Lord Maul captured the crew of the rebel starship Ghost because he knew that the Jedi members of the crew, Kanan Jarrus and Ezra Bridger, had both a Jedi and a Sith holocron in their possession. Maul had encountered the two Jedi previously. He held the other Spectres, Hera Syndulla, Sabine Wren, Garazeb Orrelios and Chopper, hostage on the ship with the help of reprogrammed tour guide droids in order to force the two Jedi to retrieve the Sith holocron, which Kanan had left with a mysterious Force wielder called the Bendu. Kanan's Jedi holocron was in his cabin on the Ghost where he always kept it. After retrieving the Sith holocron, Kanan and Ezra were told of holocron fusions by the Bendu, who warned of the incredible damage they could do. The two Jedi met Maul at Vizsla Keep 09, where he had taken the Ghost. After attempting to kill Kanan and ordering his droids to execute the prisoners, Maul had Ezra, who had been immediately escorted to the station's control room, start the fusion with him. Ezra wanted to find "the key to destroying the Sith", while Maul claimed he only wanted "hope". The ex-Sith actually wanted to find out if his archenemy Obi-Wan Kenobi was still alive and if he was, where he was hiding so Maul could find and kill him.
As the two were going deeper into the fusion, the other Spectres arrived at the control room. Kanan advised Ezra to look away, reminding him of the Bendu's warning, and the Padawan eventually did, cutting the fusion short and destroying the holocrons. Maul discovered that Kenobi was still alive, but Ezra was left with a collection of visions of places, only some of which he was familiar with.
As the fusion had been cut short, Maul and Ezra were left with the information mixed up between them. Maul was left with the location of Chopper Base on Atollon, which the Spectres and Phoenix Cell operated out of. He tracked Ezra and Kanan down on the planet some time later, and persuaded Ezra to come to Dathomir to participate in a ritual which would give them each the information they had been searching for. Doing so, Maul found out that Kenobi was on Tatooine, and Ezra saw that the Jedi Master was the key to destroying the Sith. Months later, Maul, unable to find Kenobi in Tatooine's endless desert, used a fragment of the Sith holocron he had taken to lure Ezra to the planet. The plan worked, and Ezra and Chopper became lost and nearly died, calling Kenobi out of hiding to help them. When Ezra insisted that Kenobi was the key to destroying the Sith, because of what the fusion had told him, the Jedi Master told him that Maul's desires had skewed the fusion, showing Ezra what the ex-Sith had wanted to see. Ezra and Chopper were sent on their way back to Atollon just after Maul arrived, and Kenobi killed the weakened darksider in a duel.
- Star Wars Rebels – "The Holocrons of Fate" (First appearance)
- Star Wars Rebels – "Visions and Voices" (Mentioned only)
- Star Wars Rebels – "Twin Suns" (Mentioned only)
- Unlimited Power (First identified as Holocron fusion)