Interphase cloaking device

An interphase cloaking devices or phase cloak was a type of advanced cloaking device which not only made the user invisible but also allowed them to mass through solid matter.

The Federation was successful in secretly developing the technology in 2358, however the test ship for the device the USS Pegasus (NCC-53847) was lost. The Pegasus was rediscovered in an asteroid field in 2370 where the USS Enterprise (NCC-1701-D) recovered and used the interphase cloak before making its existence known to a Romulan Warbird in the vicinity. This event was quite illegal under the Treaty of Algeron and further use and development was prohibited. (TNG episode: "The Pegasus")

The Klingons also tried to develop there own Phase cloak in 2360s but abandoned the experiments after several accidents. (TNG episode: "The Next Phase")

The Romulans were also know to have experimented with phase cloaked, experiments which after some accidents bore success. By 2376 the empire was implementing phase cloaks in Tal Shiar vessels. (TNG episode: "The Next Phase"; video game: Armada)

In the Delta Quadrant the Srivani and Voth both used the technology. (VOY episodes: "Scientific Method", "Distant Origin")