Cosmo was a former test animal of the Soviet Space Program. He was launched into Earth's orbit as part of an experiment but he drifted off into space at some point during the 1960's, arriving in Knowhere and at some point being mutated, he eventually came to serve as the station's security chief.
Cosmo met a distraught Nova shortly after he witnessed Suspensor turn into a zombie. He tells Nova that he's on Knowhere, a city right inside the severed head of a giant Celestial. Beings from all over the universe come to Knowhere, waiting for the end of the universe. Right now, the city's population had to go into hiding right after the Luminals brought something in a big box. Worldmind then informs Rider that he had deciphered the writing on the wall, which is a countdown to a timer.
Suspensor attacks them and he is forced to kill her in self defense only to have her allies Cynosure, Crater and Discharge blame him for her death. Unable to fight the three aliens, as he retreats he makes a discovery of a talking dog. However, Cosmo gained Nova’s trust and friendship, and the two set out to find the fiend responsible for all the recent deaths on Knowhere.
Cosmo brought Nova up to speed on when the events started, and the Xandarian Worldmind added any data he had at his disposal. Cosmo was mainly concerned with the safety of the remaining citizens of Knowhere who were safely hidden away in a dimensional envelope he wore on his collar. It was not long before Cosmo and Nova were ambushed by more zombies including the surviving members of Suspensor's former team, the Luminals, and determined that the creature known as Abyss was behind the mayhem. Together, they fought off the attacks, sealed Abyss inside his prison.
Cosmo then charted a course to the birthplace of the Phalanx, the planet Kvch, in hopes that he can find a way to cure himself of the Transmode Virus that is slowly killing him. Then alarms were triggered when a murderous Gamora and Drax, now under the control of the Phalanx, slaughtered many residents in search of Nova. Cosmo arrived too late to stop them before they could follow the same path as Nova through the Continuum Cortex.
He was last seen injured, after Captain Skaarn's takeover of Knowhere. Skaarn had poisoned Cosmo and shot him with something that dampened Cosmo's psychic telepathy. Using the Nova Force, the young Nova tried to push the poison out of his body. In the process, he found the foreign body inside of the psychic dog that disrupted his powers, and thus, saving him.
Telekinesis: Cosmo was an incredibly gifted telekinetic, and was capable of amazingly precise use of his telekinesis.
Telepathy: He can read and manipulate the minds of others and even higher order animals. He has demonstrated the following specialized uses:
Telepathic Defense: He can manifest his telepathy in a number of defensive ways.
Telepathic Cloak: He can mask his presence and the use of his abilities from being detected by other psions and psychic entities. He can extend these defenses to others around him as well. Cloaking via telepathy is not perfect and powerful telepaths may notice and 'see' through this ability.
Psionic Shield: Ability to erect a psychic shield for protection of himself and of others minds.
Telepathic Illusions: He can create realistic and very detailed illusions and cause people to experience events which are not actually occurring.
Telepathic Camouflage: He can alter the apparent physical appearance of himself and other people by altering the perceptions of those around him. This can go so far as to make other people believe that the camouflaged people are not there e.g. invisible.
Telepathic Manipulation: He can manipulate other people's minds easily, achieving a variety of effects.
Mind Control: He can control the thoughts and actions of others.
Mental Paralysis: He can induce temporary mental or physical paralysis.
Mental Amnesia: He can erase any awareness of particular memories or cause total amnesia.
Mental Sedating: Can telepathically "sedate" his victims so that, if already rendered unconscious, they remain so for as long as he continues to "sedate" them.
Psionic Blast: He can project psionic force bolts which have no physical effects but which can affect a victim's mind so as to cause the victim pain or unconsciousness, force then to suffer from a stroke, and turning someone brain-dead.
Mental Detection: He can sense the presence of another superhuman within a small but as yet undefined radius of himself by perceiving the distinctive mental radiations emitted by such a being.
Extended Longevity: Cosmo is decades older than the normal maximum life expectancy of a dog.