Mesla

Mesla was an Orion Klingon Defense Force Captain that opposed the crew of the USS Constance starting in 2409 (Star Trek: Constance)

Early Life
Mesla had lost her family at an early age under unknown circumstances, as a result when the Orions made an alliance with the Klingons in the late 24th century, she was one of a number of slaves given to the Great Houses.

At some point, she managed to seduce a Klingon General in the KDF, and was freed. She was allowed to enter the KDF, and would rise to the rank of Captain quickly.

She seemed to consider males nothing more than cannon fodder, putting women in most of the crutial roles on her ship.

The IKS Mish'ra
In 2409, Mesla was in command of the IKS Mish'ra when they where called to the planet Fenra IV to attempt to bring the Fenarans into the Klingon Empire. After a showdown with the USS Constance in orbit around the planet, she and her crew retreated more out of spite than anything else.

Questionable Loyalty
Mesla being an Orion, had very little loyalty to the Klingon Empire, and even less to the Orion Syndicate. Despite lack of any real evidence, it is possible that she was a spy for a mysterious faction within Starfleet, and may be part of a radical plan to restore peace between the Federation and the Klingon Empire.