The Unopans (orange humanoids that have one eyes) barely escaped Viltrumites (a race of super powerful eugenic aliens obsessed with conquering the universe) destroying them. They started a program to create a super-Unopans. Allen was the only success. After failing to fight off a single Viltrumite, he took the guise of a "Champion Evaluation Officer" and looked for beings powerful enough to fight Viltrumites. Having mistaken Earth for the planet Urath, he battled the heroes Omni-Man and his son Invincible (the main character) until the latter explained his mistake. When Allen went to his superiors at the capital of the Coalition of Planets (an anti-Viltrumite alliance), he discovered that there was an Viltrumite on Earth. When he returned to Earth, Invincible explained Omni-Man was the Viltrumite and he left his post. He return to his superiors to tell them about this since no known Viltrumite had ever left his post or had an offspring with another species let alone both. After telling his superiors the news, several Viltrumites attacked him and asked about Omni-Man. They attempted to beat him to death when he refused. He survived due to being placed in a stasis-pod, which allowed him to heal up. After months, he woke up and accidentally destroyed the pod. Thaedus, the top dog of the Coalition, revealed he was a Viltrumite rebel, Allen is strong enough to fight a Viltrumite and there was a mole. As such, Allen was ordered to report to him directly. Allen visited Invincible, who told Allen about Omni-Man's capture, his half-brother (the half-Viltrumite Oliver) and Omni-Man's "science fiction" novels hid some secret to stop the Viltrumites. On the way back, Allen allowed himself to be captured by a Viltrumite so he could free Omni-Man. When balking to Omni-Man via his telepathic powers, he befriends Omni-Man and gets him up-to-date. He also mentioned an upcoming Viltrumite-Coalition war. Allen convinced Omni-Man to help the Coalition. They (and another prisoner Battle Beast) escaped and Nolan (Omni-Man) revealed less than 50 pure blood Viltrumite exist (their eugenic practices killed 99.9% of the population). They headed to the Coalition. Allen allowed Nolan to live in his apartment. Nolan freed his former enemy Space Racer (who was mentioned his books), who has a gun that can shoot through anything. Nolan, Space Racer and Allen did various missions. The war started. Allen and Nolan convinced Invincible, Allen and Tech Jacket to help them. Omni-Man and his sons got separated. Allen and Tech Jacket went to the Coalition. There the Viltrumites attacked and the mole was found. Omni-Man and his sons came to help the Coalition. The attacking Viltrumites and Thaedus were killed by the Coalition thus winning the war. Allen became the leader of the Coalition. He had Invincible search Earth for any remaining Viltrumite and was doing similar things for all the other Viltrumites-conquered plants. Allen discovered the "Scourge Virus" can kill every single Viltrumite, but finds a note telling him not to use oi. Viltrumites were on Earth, but Nolan and Allen were split on how do deal with them: Nolan believed they could change like he did, but Allen thought they should be killed by the virus. Allen revealed to Nolan that he knows the virus might kill humanity. Allen planned to do this anyway and attacked Nolan for trying to stop him.
Allen's main powers are super strength, reflexes, speed, healing and durability; near-light speed flight; immunity to decompression; and telepathy. He discovered he is immortal and that "killing" him makes him stronger (although this has minimal affects of his appearance).