The Zetarians originally came from the planet Zetar. They boasted a large humanoid population. The race faced extinction and only about 100 survivors escaped. These survivors now live in a noncorporeal state.
In their current state, it appeared that they are a multicolored cloud of lights. This cloud emitted high-intensity and was often mistaken for a natural occurrence.
The cloud was sentient through. It could travel warp speeds of about 2.3. It also registered as life forms on sensors.
They looked for minds for them to lock onto. They needed minds that were easily adaptable. Once in control of the body, they could speak through the victim and communicate through others.
At first, it sounded like gibberish coming from the victim’s mouth then their face began to change color.
There was two outcomes of what would happen, either the victim accepted being taken over and fight the intrusion. They often suffered severe brain damage. When the victim offered less resistance, the Zetarians’ voices could be heard through the victim.
The last remaining Zetarians were destroyed by the U.S.S. Enterprise in 2269. This ocurred after the Zetarians attacked Federation facilities and personnel.