A highly advanced species living beyond the galactic barrier whose mining device, the Dark Matter Anomaly, caused catastrophic damage across the galaxy.
Species 10-C is the name Starfleet gives to an unknown civilisation that lives beyond the galactic barrier in a vast hyperfield. They are enormous beings who communicate through mathematics, light and complex chemical signals rather than speech. They do not seem to understand at first that other forms of intelligent life are present in the galaxy.
In the fourth season of Star Trek: Discovery, set in 3189 and 3190, a gravitational anomaly appears without warning, destroying worlds including Kwejian, the home of Cleveland Booker. Michael Burnham and the crew of USS Discovery trace it to Species 10-C, which uses the device to mine the rare element boronite. Discovery travels beyond the barrier and, working with experts from across the Federation, manages to establish communication.
The first contact is fraught, as Booker and the scientist Ruon Tarka try to destroy the device on their own. Burnham persuades Species 10-C that the galaxy is full of life, and the beings agree to stop. The arc stands out for treating first contact as a slow puzzle in understanding.