Odo is a changeling, a shape-shifting being made of a gelatinous fluid. He serves as the Chief of Security aboard the space station Deep Space 9, a role he fulfills taking on a humanoid shape in order to fit in to a degree with the station's population. Odo is regarded by DS9's inhabitants as being the best officer of the law in the Bajoran sector and beyond. He sees himself as a sentinel of order and goes to great lengths to maintain that order, though he has been known to bend Starfleet rules occasionally to better perform his duties. He is portrayed by Rene Auberjonois.
Odo in the Mirror Universe[]
In the DS9 episode "Crossover", Dr. Julian Bashir and Major Kira Nerys somehow end up in a parallel universe after traversing the Bajoran Wormhole. They arrive at Terok Nor, an alternate version of their Deep Space 9, where they meet several counterparts of people from their own universe, including Odo.
The mirror Odo serves as Terok Nor's security chief, but the main difference between him and Odo Prime is that he takes a sadistic pleasure out of his job. Rather than serving as a mere policeman on the station's promenade, he is a ruthless slave driver who works Terrans to death in the station's ore processing plants.
Mirror Odo explodes after being shot with a phaser.
During the episode, a thorium leak occurred in the ore plant and the workers were evacuated. In the confusion, Dr. Bashir snatched a phaser from one of the guards, setting it to kill and firing on Odo. Odo exploded in a shower of congealed goo.