SK-21 support droids were droids produced on the planet Mustafar by the rogue assassin droid HK-47 to support his droid army. Their design was based on that of HK-47. Several of them were destroyed in the crater of a volcano by a group of spacers that fought against HK-47 and his droids.

Behind the scenesEdit

The SK-21 support droids' first and only appearance was in Trials of Obi-Wan, the third expansion for Sony Online Entertainment's MMORPG Star Wars Galaxies. It appeared during the final stage of the Champion of Mustafar quest line that takes place in the crater of a volcano and pits a group of players against HK-47 and his droids.

It is unclear whether these droids were designed by the Separatists on Mustafar based on HK-47's body they found in the wreckage of a crashed Hammerhead-class cruiser or by HK-47 himself after he gained control of the Separatists' old droid factory.