COMPANION

Presumed planet of origin:  a planetoid in an asteroid belt located in the Gamma Canaris star system, less than 1000 ly from Earth, possibly a remnant of a planet breakup. It is one of 7000 bodies  in the asteroid belt, 34 % of which had some type of atmosphere. The composition of the planetoid is iron and nickel, and it had an atmosphere that consisted primarily of oxygen and nitrogen with traces of krypton, argon, and neon. The general surface temperature was 75 °F. Gravity was 1G.

Only one representative of this species is known. The Companion is a non humanoid lifeform  composed chiefly of ionized hydrogen and electricity. It appeared as a gaseous, vaguely sparkling cloud of yellow, orange, and red.It is able to communicate via telepathy with willing to do so. It has the ability to rejuvenate organic life, and inhibit the aging process, disperse or teleport itsel, produce material objects, including food and water and manipulate objects through telekynesis, produce electric discharges. It can also merge with a humanoid, creating a joined entity. In doing this, the creature sacrifices its immortality and most of its other powers. 

Source: Star Trek universe,  (TOS: "Metamorphosis")

UNNAMED ALIEN IN A FOREST

NIMONS / MINOTAURS

The Minotaurs are a minotaur-like humanoid species that developed a parasitic spacefaring civilisation on an interstellar scale. Parasitic by nature,  they fed on the faith of other life forms and survived by descending on primitive planets, setting themselves up as gods to feed on the worship of the natives. They could not feed on a person who held no strong beliefs. After a while when species became advanced, they usually managed to expell them upon realising their true nature.
A more dangerous offshoot of the species, called Nimon, could effectively drain not only faith but the very life force of their victim and could shoot blasts of energy from their horns. The Nimons were able to consume to extinction the population of an entire world within a few years. As their food source got scarce, they would look for another planet ripe for conquest and draining. A scout would descend on a planet, representing itself as a god with gifts of  advanced technology and start to construct a maze-like Power Complex  designed to generate a portal back to the Nimons' current planet. The Nimons would then migrate en masse to the new planet using capsules sent through the portal,  drain that world dry and look for the next, continuing the cycle they referred to as the Great Journey of Life.
They are said to have been one of many races that participated in the Millennial War some 150 million years ago against the Mad Mind of Bophemeral where they collaborated with the Osirians in dropping quantum collapsers on the insane computer intelligence. (PDA: The Quantum Archangel). At some point after the third millenium, after having drained the planet Crinoth, all traces of them was lost while they were travelling via their their portal toward their next prey, the planet Skonnos.
Source: Doctor Who universe,    (DW: The Horns of Nimon)  (DW: The God Complex)

YIRBEK

Planet of origin: Yirb, a planet in the Bek star system in the Andromeda galaxy.

They Yirbek are reptilian bipeds which developed an spacefaring civilisation and built a small interstellar empire before being conquered by the Skrulls some centuries before the third millenium. They have since then been used by their masters as mercenaries in minor galactic conflicts.

Source:  Marvel universe, Created by Stan Lee, Larry Lieber, Paul Laiken, Jack Kirby and Don Heck.  Avengers #14 ( march 1965)

HUSNOCK

The Husnock were an highly agressive species which developed and interstellar civilisation in the Milky Way galaxy with a population of over fifty billion before being eradicated in a split second by a Douwd after they had wiped out an Earth colony on which it was secretly living in 2366.
Source: Star Trek Universe (TNG: "The Survivors")

DOUWD

The Douwd are a peaceful immortal extragalactic uncorporeal species, self-described as "beings of disguises and false surroundings". Through their uncanny psychic powers, they have the ability to create and destroy on an interstellar scale and maybe more. Although they can't bring people back to life, they can make illusionary recreations of them. Although seamingly nearly omnipotent, they are not omniscient.

One Douwd has been known to travel the Milky Way,sometimes under the form of a human in the course of the 24th century. During that time, he destroyesd the Husnock civilisation after they had wiped out a human colony on which he was living.

Source: Star Trek universe, (TNG: "The Survivors")

ALIEN CREATURE LOOKING AT THE CAMERA

Originally posted on Ghislain Barbe's blog Qosmiq for the People.