(Official Handbook of the Marvel Universe Deluxe Edition I#16) - Rieg Davan underwent special training in the Syfon Warrior division of the Nova Corps. He became one of the division's most adept operatives.
(Nova I#24 (fb) ) - Davan was ordered by imperial suzerain Adora to take his space ship to investigate rumors Xandar was facing an invasion. Out on patrol, his ship collided with a comet that caused severe damage. Davan drifted in space for months, helpless with the knowledge the invasion of Xandar had most likely occurred already.
(Nova I#2 (fb) - BTS) - Davan's spaceship eventually crashed in one of Earth's oceans. Suffering from amnesia, he was rescued by the villainous Condor who saw a use for Davan and his powers in his fight against the Sphinx.
(Nova I#6 (fb) ) - Hoping to bind Powerhouse to him, the Condor told him that his absorption powers had caused him to siphon off all the life aboard a nearby shipwreck. Fearing he was now a wanted criminal, the confused and amnesiac Powerhouse agreed to work with the Condor.
(Nova I#2) - The belligerent Condor was most displeased when he returned to his Roost and found Powerhouse wasn't there to greet him. He sought out the youth who was wandering outside, smacking him around to do his bidding. He forced Davan to put on his costume as they sought out the new, powerful young hero Nova. Condor had Davan absorb as much of Nova's power as he could in preparation for their inevitable confrontation with the Sphinx. In the next phase of their plan, Condor took Powerhouse to a nearby museum to retrieve vital information from a sarcophagus on display. Nova intervened and Davan accidentally destroyed the sarcophagus with the information, making the Condor so furious he abandoned him. This left Powerhouse so distraught, it allowed Nova to punch him out.
(Nova I#6 (fb) - BTS)
- Nova took the unconscious, but still dangerous Powerhouse to the
police. They took him to the hospital where his power draining abilities
were negated by placing him inside an absorbatron which also kept him
unconscious. (Nova I#6) - Still feeling Powerhouse could be useful, Condor and his new ally Diamondhead invaded the hospital to break him out. Nova picked up the distress call one of the nurses sent out and decided to intervene. However, he was overcome by the Condor and his petrifying gas. Both Powerhouse and Nova were taken to the Condor's Roost where the villain put Davan in his old costume again. Davan immediately tried to resist serving the Condor, but he brutally beat him back into submission. Powerhouse then watched Condor probe Nova's mind using his computalyzer.
(Nova I#6) - The Condor learned of the existence of Nova's Xandarian spaceship in orbit around Earth. He was eager to access its databanks to help him in his quest. However, Powerhouse rebelled and siphoned off sufficient current to disrupt the computalyzer. This freed Nova and led to Condor and Diamondhead pounding both teens until they behaved again. Nova was placed back in the computalyzer and subjected to a mind control procedure. However, as a result Nova turned evil and assumed control of the Terrible Trio.
(Nova I#6 - BTS) - Unbeknownst to Powerhouse, Nova and the others, the Sphinx was observing their progress from his fortress, planning appropriate countermeasures to their plans.
(Nova I#7) - After some
predictable infighting, Condor told Powerhouse, Nova and Diamondhead of
the foe he had been preparing for: the Sphinx, a 5000 year old foe from
ancient Egypt who had come to the United States to spread terror and
become Lord of Crime, a title Condor felt belonged to him. (Nova I#7 - BTS) - Sphinx observed the Condor's rant and had to laugh because his opponent had no idea of his true objective: become emperor of the world itself. Powerhouse stayed behind while Nova and the Condor flew off to steal a component needed for the Condor's craft to reach the Nova Prime ship.
(Nova I#7) - Upon returning to the Roost, Nova's mind control began to fade, forcing Powerhouse to drain some more power until Condor could put their new ally in the computalyzer again. Seeing Nova get reconditioned made Powerhouse realize this may well have been the same method through which Condor had turned him into a helpless accomplice. Powerhouse joined the others as they flew to the Nova Prime ship, with Nova using the technology in his helmet to gain access to the vessel.
(Nova I#7 - BTS) - Sphinx grew concerned that Powerhouse, Condor and the others were gaining an advantage over him by plundering the alien vessel. Redirecting the energies of his Ka stone into space, he managed to activate and control the ship's defenses.
(Nova I#7) - Condor led Powerhouse and the others in their battle against the various robots and internal defenses. Powerhouse absorbed so much energy, he was about to explode but Condor ordered him to redirect the energies to blast open the armored door to the ship's armory. At that same moment, Nova freed himself from his mind control once more and attacked Condor. Powerhouse refused a direct order to attack Nova, but still followed Condor in raiding the armory and escaping with weapons to use against the Sphinx. Nova was left alone in his ship, seemingly unable to escape.
(Nova I#8 - BTS) -Using the Nova Prime ship's computers, Nova saw footage of Powerhouse, Condor and Diamondhead attacking the Sphinx's palace, blasting his troops with the Xandarian weapons they'd stolen.
(Nova I#10) - During
the assault on the Sphinx's palace, Powerhouse noticed he couldn't drain
the villain's henchmen of their energies, learning they were actually
empty shells. Alerted by his aide Kur, the Sphinx involved himself in
the battle, revealing the true shape of his base as the pyramid of
knowledge. Taking on the Sphinx outside, all combatants were surprised
when Nova showed up to join the fight (he had learned the Condor's
location through the computers of his ship). Powerhouse managed to
drain some of the Sphinx's energies, but the villain was still strong
enough to knock out Diamondhead. Powerhouse then focused on Nova,
fighting him to a near standstill and siphoning off enough energy to
leave them both vulnerable to the Sphinx who had not only survived an
assassination attempt by the treacherous Kur, he also transformed Condor
into his avian namesake. Sphinx decided to take in Powerhouse and Nova
to probe their minds in hopes of finding an answer to the one question
that kept plaguing his existence for millennia. (Nova I#11) - Probing the mind of Nova, the Sphinx was frustrated to learn that the young hero possessed the answer, but his Nova powers prevented anyone from accessing his mind or even force him to give information under duress. Frustrated, the Sphinx chose an unusual tactic. He wiped Richard Rider's mind of any knowledge of being Nova and sent him home, planning to get the answer from him when his mind was less guarded. Seeing no further use for Powerhouse, he mindwiped him too and transported him to London. Regaining consciousness, Rieg Davan was once again totally lost in an unfamiliar world.
(Nova I#24 (fb) - BTS) - Davan survived for months as a derelict on the streets of London.
(Nova I#24) - Sphinx sent Nova to collect Powerhouse. Seeing Nova instantly made him regain most of his memories and in the ensuing brawl the two young heroes caused massive damage to the city before the Sphinx retrieved them both with a teleportation beam. Joined on board by Dr. Sun, Crime-Buster and Comet, Nova and Powerhouse were brought before the Sphinx who restored Rieg Davan's full memory. Now aware he was a Xandarian, he instantly recognized Nova's vessel as a Centurion starship.
(Nova I#24 - BTS) - No one realized Diamondhead had snuck aboard the Sphinx' ship by stowing away on Crime-Buster's pod ship.
(Nova I#25) -
Powerhouse effortlessly piloted Nova's starship towards Xandar,
space-phasing the craft to reach the planet in the first quadrant of the
Andromeda galaxy. He warned off the secretive Dr. Sun when he attempted
to access the forbidden knowledge of the ship's computers, but their
argument was cut short when Diamondhead revealed himself. Before
Powerhouse could act, Sphinx reduced the villain to rubble, promising to
restore him to teach him a lesson. Just then, the ship ran into an
attacking Skrull armada. Powerhouse left Crime-Buster to mind the
controls while he joined Nova and the Sphinx outside to deal with the
Skrulls. Nova was impressed when Davan used the full extent of his
abilities to easily blow up entire ships. The battle ended when the
surviving Skrull fleet beat a retreat. Gathering all their forces back
inside the ship, it was decided to hightail it to Xandar before the
Skrulls would return. 
(Fantastic Four I#209) - Powerhouse
watched from the side as Mr. Fantastic used the Xandarian Worldmind's
knowledge to quickly construct a miniature, sentient robot that he
dubbed H.E.R.B.I.E. which was tasked to help the team locate Galactus,
whom Mr. Fantastic figured would be the only one able to stop the
Sphinx. The FF asked Nova, Powerhouse the remaining heroes of Earth to
stand together as the new Champions of Xandar against the ever present
Skrull threat while the Fantastic Four tried to save Earth from the
Sphinx. Not too long after that, Powerhouse and the other Xandarians
learned that the Skrulls had pulled back all of their forces in
preparation for one, final attack on Xandar. 
(Avengers I#260 (fb) - BTS) -
Powerhouse, the Champions and all of Xandar perished when Nebula
attacked the world aboard Sanctuary II, the mobile space fortress
created by her alleged grandfather, Thanos of Titan.