In appearance, Ktarians are mostly humanoid and are from a fairly advanced culture. Their distinguishing features include a slightly enlarged front cranium formed into two circular halves, separated by a shallow crease in the skin, which makes them appear almost cat-like. The also have scales on some parts of their body. Ktarian children develop much faster than human children do.

Ktarian natives lay thousands of stones, each representing a separate prayer, around the tomb of their dead loved ones.

On stardate 45208.2, the Ktarians launched an ambitious plan to attempt to seize control of a Federation starship, and eventually of the Federation itself. Though not a galactic power, their dream of an "expansion" take-over includes bypassing the superior firepower of the Federation with the help of an extremely addictive mind-control "game."

As seen with the antique plasma coil on display at Deep Space Nine, they had interstellar flight 300 years ago (2060s), before the invention of warp drive by Zephram Cochran. They were known to mainstream Federation at least 80 years ago, circa 2293.