Spirit gates are tears opened into the spiritstream via a spirit well. The only race with the ability to open these wells are the Charu.
The Charu were able to enter the spiritstream with their spirits. Inside the stream, the Charu were able to feel the weaknesses caused by spirit wells as they traversed the mirror universe.
The discovery of Uthrac, a planet similar to their own, brought excitement to their race. On Uthrac, the Charu discovered two spirit wells.
Many theories were made as to how one could traverse the two worlds by using the spirit wells.