- "We do not recognize your authority!"
- ―The hex droid response to all queries
Fastbreeders, also known colloquially as Hex droids or simply hexes, were a model of combat droid designed and created by Lema Xandret, a Human female who fled the Sith Empire after attempting to prevent the Sith from taking her daughter, Cinzia, from her to be trained as a Sith. Xandret later cloned her daughter on the remote planet Sebaddon and named the clone Cinzia as well, before assigning the hexes to protect her at all costs. The droids were instilled with a remnant of Lema Xandret, known as an amnioid, which gave them life-like qualities. The droids were obsessed with protecting Cinzia, and took whatever measures necessary to ensure her survival—including killing Xandret, their creator.
They were eventually discovered by the outer galaxy, and a hex droid nest was captured and put on auction by the Hutt Tassaa Bareesh. When several of the auctions' attendees attempted to steal the nest, a skirmish began. Several of the hex droids emerged from the hex droid nest and joined the skirmish. To do so, they melted right through the vault door.
The hexes were silver and about 2 meters high when standing on two legs. They had six appendages, and each of the appendages could be used as either legs or arms. Their bodies were hexagonal, and elongated when standing. Each appendage could be used to attack a different target at the same time. The appendages shot energy pulses of blue fire. The hexes could cross two limbs and produce a short-lived electro-mirror that was capable of turning back even a lightsaber. The sensors on the droids' bodies absorbed blaster bolts instead of reflecting them. They would dissipate the heat, but if the attacks came too quickly to dissipate the heat, the sensors could explode. The droids were also capable of cloaking themselves.
The hexes displayed remarkable adaptability during battle (with at least one being deployed unfinished and building as it fought) and immediately took the upper hand over the Sith, Jedi, and Mandalorian factions that were fighting. The Hutts' security forces also joined the battle. Certain parts of the Hexes' surface could reflect blaster bolts. Even blasts from a heavy blaster turret could be reflected, and the droids reflected those heavier blasts toward the walls with the intention of breaking out of the vault. Their limbs were not as protected, however, and eventually the other factions joined forces to defeat those few hex droids that emerged from the nest. The Sith and Republic were able to trace the hexes back to Sebaddon, and they each traveled there separately. Upon arrival, their fleets were attacked by the hexes, which took control of their ships and caused them to turn on one another.
The Republic and Empire then allied briefly for a mission to destroy the hexes before the hexes could take over the galaxy. After all, total control of the galaxy would be the best way to protect Cinzia. During the mission, the original Cinzia—now a Sith apprentice under the name of Eldon Ax—in the company of Jedi Grand Master Satele Shan, found the clone, who was kept in a Force–free bacta tank, also with the amnioid inside of it.
When the amnioid turned on Cinzia, attempting to keep her under control and prevent her from listening to reasoning from Shan. Ax destroyed the tank holding the clone to free her, but Cinzia was killed by the shock of being freed from the tank and unable to breath air. Ax then took control of the hex droids and used them to kill her Master, Darth Chratis, before allowing them to destroy themselves, as, with Cinzia's death, they had nothing left for which to live.
- The Old Republic: Fatal Alliance (First appearance)