IO-98-D was the identifier assigned to a droid processor that served the Galactic Empire. Darth Vader, a Sith Lord, employed this droid brain, along with others, to manipulate the M.A.R. Corps, a group of cyborg rebels; IO-98-D was placed inside Masakint. In the course of a battle with one-time governor Tauntaza, the cyborg's connection to the droid brain was severed, briefly granting them autonomy, which they used to oppose Vader. The Sith then used the Force to reestablish the link to the droid brain, which expressed its gratitude.