Terran Empire flagship of the mirror universe, a vast vessel powered by a mycelial reactor and the seat of Emperor Georgiou.
The ISS Charon was the flagship of the Terran Empire in the mirror universe, an enormous vessel built around a glowing sphere that housed a mycelial reactor. It served as the throne ship of Emperor Philippa Georgiou and the seat of imperial power.
In Vaulting Ambition, Michael Burnham came aboard posing as her mirror counterpart and bringing Captain Gabriel Lorca as a prisoner, only to learn that Lorca was himself a Terran from the mirror universe who had once tried to overthrow the Emperor. In What's Past Is Prologue, Lorca escaped, freed his followers and seized control of the ship.
The mycelial reactor was poisoning the mycelial network across all universes. After Georgiou killed Lorca and Burnham escaped with the Emperor, Discovery fired into the reactor and destroyed the Charon, riding the resulting shockwave back to its own universe.