A Klingon colony near the Federation border whose rebellion the Romulans tried to use to set the Klingons against the Federation.
Krios is a Klingon colony world close to Federation space, governed by Vagh and troubled by a rebel movement.
In The Mind's Eye, Vagh claims that Federation weapons have reached the Krios rebels, and the Enterprise investigates alongside Ambassador Kell. The weapons prove to be Romulan replicas, and the plot is traced to Kell and to the brainwashed La Forge, preventing a break between the two powers. The affair shows how far the Romulans were prepared to go to divide their rivals.