GT 6

After the Ancient Gate Network was discovered and activated. It became apparent Trans Spatial Gates had been built and left behind by several spacefaring societies and entities. The technology, age and reason for the gates vary greatly. The Science Council assigned the Science Corps Xeno Tech department to increase research on all Alien Gates. One of the immediate results of this research was a classification system See also GATE TYPE , GT 1, GT 2, GT 3 , GT 4, GT 5, GT 6, GT 7, GT 8, GT 9, GT 10

GT 6 - Ghost Gates. Unknown gates that suddenly appear aka Rumor Gates

There are rumors and stories of Long distant traders and space farers about  ghost and Phantom gates that sudenly appear and send ships in far distant regions. There are of course the rare but occationally observed Worm Holes (Never stable enough to be utilized) And stores about other ancient species who left gates behind.

Example: The Back Door Gate in the shattered star system before its official discovery