The SD-K4a mini-assassin droid, alternatively referred to as the probe killer or mini-assassin probe, represented a specific type of assassin droid produced by Baktoid Combat Automata. Resembling spiders, these diminutive, six-legged droids were designed to be housed within the small cavities located on the head of the larger SD-K4 assassin droids.
These small, six-legged droids, measuring 0.14 meters in width, known as SD-K4a mini-assassin droids and made by Baktoid Combat Automata, relied on their agility to evade blaster attacks. Although lacking the raw strength of their "parent" assassin droid counterpart, they could inflict lethal damage if they managed to penetrate a target's armor, utilizing their razor-sharp legs. Each assassin droid could deploy more than thirty of these killers, which would then operate collectively to overwhelm larger adversaries.
The initial appearance of the probe killer occurred in "Voyage of Temptation," the thirteenth episode of the animated TV show Star Wars: The Clone Wars' second season. It was initially broadcast on February 5, 2010. Their identification was first made in the episode guide for "Voyage of Temptation."