Thasian

From Memory Alpha, the free Star Trek reference.

The Thasians are a race of non-corporeal, psionically-powerful beings believed to be native to the planet Thasus. The Federation had encountered them only once, in 2266.

A Human named Charles Evans was the only survivor of a crash-landing on the planet Thasus. Because he was young and the planet was inhospitable to Humans, the Thasians granted him considerable psionic powers so that he might survive.

After Evans was rescued from Thasus, he misused his powers and caused considerable trouble. The Thasians located him after he had used his powers to take control of the USS Enterprise. At close range, they had no difficulty preventing him from using the abilities they had granted him; this suggests they possessed at least the same powers as they granted Evans. One Thasian rematerialized people and objects previously dematerialized by Evans. It also transported itself to the Enterprise (or possibly projected an image of itself), and transported Evans from the Enterprise to its own ship.

Thasians have the power to confer psionic ability on other beings. Once they have done so, they either cannot or will not remove this power. When Captain Kirk suggested that Evans belonged with his own people, the Thasian said "That would be impossible." When Kirk suggested Evans might be trained not to use his powers, the Thasian replied that "We gave him the power so he could live. He will use it – always." The Thasian then removed Evans from the Enterprise and disappeared with him, saying they offered him life, and would take care of him.

Thasians travel through space within a glowing construct that is apparently their version of a space vessel. This does not seem to traverse space linearly, instead materializing and dematerializing. Sensors can detect this construct, but deflectors indicate no solid substance.

The Thasian encountered in 2266 appeared as a translucent, floating Human face approximately one meter tall that wavered and rippled constantly. It stated that it had taken its form from centuries ago so that it might communicate with Humans. This is therefore unlikely to be the true form of most Thasians, and it may be that they can change forms only with difficulty. (TOS: "Charlie X")

The Thasian was portrayed by Abraham Sofaer.