Wikipedia
Coeurl is a fictional alien race of predators created by science fiction novelist A. E. van Vogt (1912-2000) and featured in his first published short story "Black Destroyer" (1939), later incorporated in the novel The Voyage of the Space Beagle (1950). Its appearance is comparable to a large cat, except that its forelegs are twice as long as its hind legs, and it possesses tentacles (most likely two) attached to its shoulders that terminate in suction cups. Its skin coloration is not mentioned but, in addition to the story title, is also depicted as black in the cover art for the original magazine appearance. It sustains itself by feeding upon a substance it calls the Id of other beings, which is not related to the Freudian concept but is actually organic phosphorus, most probably as the phosphate groups bound in ATP.
It appears indifferent to environment and can survive in different atmospheres. It also has the ability to manipulate EM radiation (referred to as "electric vibrations" in the story) at will, and seems to communicate via this method.
In "Black Destroyer", a sentient creature that calls itself Coeurl lives on an alien planet, feeding on the id of local creatures. When a human starship arrives on the planet, they find Coeurl but assume it is an unintelligent animal, and even allow it to come on board. Coeurl realizes it can feed on humans but plays along in order to learn more about them and their ship. Eventually however, it gives in to hunger and kills and feeds on one of the ship's crew. The crew suspects the Coeurl did it, and tries to prove it by feeding the creature organically-bound phosphorus similar to that in the victim's bones, but Coeurl is smart enough to pass the test. Eventually however, it is found out and tries to escape, but it is no match for the humans' technology, and in the end commits suicide.
When "Black Destroyer" was incorporated into The Voyage of the Space Beagle, several changes were made in Coeurl's anatomy and physiology—for example, Coeurl's tentacles originally ended in tentacled fingers, but were changed in the novel to suction cups, and the dietary chemical was changed from phosphorus to potassium. In the novel, it is theorized that the members of Coeurl's race were pets or servants of the original inhabitants of the planet.