The Na'kuhl are a sapient humanoid species which developed time traveling abilities at some point in the 29th century, and refused to accept the Temporal Accords commonly accepted by time-travel capable societies. Instead, the Na'kuhl believed that this technology, like any other, should be used by each species in their own benefit. They thus proceeded to travel back in time, attempting to alter galactic history in their favor, and became one of the main factions in the conflict that became known as the Temporal Cold War. Physically, the Na'kuhl resemble humanoids with pale, hairless bony skin, yellowish brown blood and red eyes.
As a result of their interfering with time - including an attempt to prevent the Suliban species from forming - the Na'kuhl were hunted by temporal agents from the 31st century Federation. At one point they managed to seek refuge on Earth in the 1940s, but became trapped there, with no temporal vehicles or other means of escape. There they interfered with history once again by allying with the Earth nation of Germany; creating an alternate timeline in which most of the western hemisphere was under German control in the 20th century. They attempted to use Earth resources to build a temporal conduit mechanism that could end their exile and allow them to continue their war for galactic dominance. Although they actually succeeded in this; temporal agents were able to track down the origin of the conduit and send Earth Starfleet officer Captain Archer back in time to destroy the conduit and restore the original timeline; which he succeeded in doing. It is implied that with the destruction of the Na'kuhl the Temporal Cold War came to an end, but it isn't clear whether the group stranded on 1944 Earth represented the only members of the species, the only ones with time travel capabilities or simply a group of renegades.