Drift Drive

Introduction
The drift drive is ancient piece of technology invented by the Illithid-Dilug Intergalactic Empire of New Rocheron that allows a vessel to planeshift into and out of a dimension known as the drift, allowing vast distances to be crossed in a matter of minutes. While it was used extensively during the Ancient Precursor Era and the High Precursor Era the drift drive is no longer used today, with people instead using the Plane Shift Drive.
Creation
The first drift drive was created 102 years after The First Cataclysm, in an attempt to expand the influence of the newly-formed Empire. The device was wildly successful and was used to rapidly explore the star systems nearby Supreme Solaris.
Replacement
According to the ancient data records of the Illithid-Dilug Intergalactic Empire of New Rocheron the drift drive was first phased out during the end of The Second Cataclysm. New ships were instead fitted with plane shift drives. However, plane shift drives were both dangerous and took a significantly longer time to travel longer distances. However, the Empire has refused to reintroduce drift drives into production.
Speculation
There have been numerous reports throughout The Modern Era of vessels using drift drives. All of the reports have the following things in common:
1: All vessels are property of the imperial government 2: No civilians were detected aboard 3: The vessels displayed other Precursor Technology 
The Empire has denied all of these claims.