Construction droid/Legends

The self-replicating construction droid was a construction droid used by the Galactic Empire for building vast structures, such as the Death Star battlestations.

Characteristics
The construction droid used raw materials to construct more droids of its kind, thus exponentially increasing the droid work force during a building project. As such, it was similar in design to the later mobile factories, the World Devastators.

History
During construction of the Death Star I, it was determined that building the station's interior structures in a piecemeal manner and allowing the greatest possible space for these droids, led to the most efficient construction. This tactic was used by Moff Jerjerrod during the Death Star II's construction period.