The White Witch was one of the first Geth "Mobile Hardware Platforms", established in after the Morning War.
The White Witch was the first Geth MHP established by the Geth in order to scout organic space shortly after the Morning War. White Witch was colored white, with red lights, a style that would later be adopted by its successor, Legion.
White Witch had up to 2,487 programs within it. And as such, was intelligent and skilled. White Witch's armor was reinforced, so that it could withstand almost anything thrown at it. This, however, did stop it from meeting its eventual fate.
White Witch encountered some of the first Collectors aboard the Derelict Reaper. It fought several days against them, sustaining large damage in the process. After up to 2 weeks of combat, White Witch was shot and disabled, before its deactivation, it saw Harbinger preparing to control a Collector.