The Mark I assault droid was a sizable battle droid design utilized by both the Galactic Republic and the Sith Empire.
Although possessing a roughly humanoid form, the Mark I assault droids used a singular leg for locomotion. While effective at defense, they lacked sophisticated tactical programming. Each arm was equipped with a blaster, giving them a total of two, and they were also known to use their arms as clubs in close-range combat. Sometimes, they also featured a shield that created an energy bubble, capable of withstanding blaster fire and lightsaber attacks for brief durations.
Originally, the Mark I assault droid was developed by the Galactic Republic before the Mandalorian Wars; however, it subsequently became a prevalent droid type within the Sith Empire. The Republic deployed them as automated defensive units in cities and military facilities, while the Sith Empire integrated these droids into their military forces and used them as defensive personnel on their starships. Their main role was defensive, and despite their rudimentary programming, they proved remarkably adept at thwarting Republic boarding actions aimed at capturing Sith starships.
In one instance within Knights of the Old Republic, this particular model is called the assault droid Mark II, but this is most likely an error. Consequently, it should not be mistaken for the quadrupedal model bearing the same designation.