The Skagarans are a warp-capable humanoid race, also known as "Skags".
During the 19th century, a Skagaran ship was sent to Earth. The vessel's crew abducted several thousand Humans that were later taken to help the Skagarans start a colony, and serve as slave workers.
In the 20th century, the Skagarans had contact with the Briori, giving knowledge of the humans as an easily enslaved species. (Star Trek: Phoenix-X: "Temporal Doom! Part II")
Skagaran article at Memory Alpha, the canon Star Trek wiki.