Daniel (mirror)

Daniel was the commanding officer aboard the secret Terran Rebellion starship Phoenix-X in 2375. He was a rogue Changeling, possibly from the Gamma Quadrant, who decided to help the opressed Terrans in favour of gaining his own command. 

Universes
In 2371, schematics for the Multi-Vector class were stolen from the primary universe by Smiley O'Brien. Over the next four and a half years, secret Terran tech teams worked on building the Phoenix-X without any of the Rebellion's knowledge, except for Smiley. During this time, Daniel had roamed into Terran territory, where he made quick allies with Smiley. To secure Daniel's help, Smiley offered the Changeling a command position on a special new ship.

When the Phoenix-X was launched in 2375, Daniel took command, along with a select crew. It didn't take long for power to corrupt the Changeling, and in less than a month the crew found themselves on the brink of destruction: the Phoenix-X had encountered a Iso-Star which brought their ship into the primary universe.

There, they met with an identical Phoenix-X, mistaking them as momentarily created duplicates. To alleviate redundancy, Daniel renamed his ship the Phoenix-V. But almost immediately, in a battle to destroy the other ship, the Phoenix-V was destroyed itself. ("Pure Evil", "Mirrorlyness!")

Eight years later, in 2383, a partial omnipotent being named Rein, entered the same in the area. Rein was attempting to increase his power by the action of using power, and brought the annihilated crew back to life aboard his Talarian starship. This action allowed Rein to ascend into another plain of existence, allowing Daniel and his crew to take over the Talarian starship.

Wanting something more powerful, Daniel tracked down the USS Fusion and hijacked it. When Rein was reminded by Q that he had brought a mirror universe crew back to life, Rein immediately sent the crew back to their own universe.

Unfortunately, back in his own universe, Daniel was met with an energy surge accident that incapacitated him and turned him into a liquid. With Daniel out of the picture, the Klingon-Cardassian Alliance sympathizers aboard the Fusion were able to take over. They quickly renamed the ship Phoenix-X, as they had previously promised to capture a similar ship with said name for thier superiors. ("Broken Pieces")