Thor while passing by sees a round of police officer in front of Roxxon Neucleonics, who alerts him that half a dozen terrorist are bottled inside with a active nuclear reactor. Thor goes to confront the terrorists and rather easily defeats them, but one of the bullets manages to hit the nuclear reactor. The nuclear reactor explodes sending Thor into 30th century , the era of Guardians of the Galaxy, where he happens to land inside Korvac's ship.
Korvac uses his machines to attack Thor, but Thor quickly destroys the machine. Korvac with a press of a button teleports Thor into deep space where Thor is frozen solid.
Guardians of the Galaxy , who happen to be flying around in Freedom's Liberty, unprovoked, get attacked by Korvac goons. They are eventually forced to flee after Korvac creates a meteor storm, travelling at near light speed, towards the ship.
While flying around Starhawk find the frozen Thor who is brought back into Freedom's Liberty (Guardian of the Galaxy's spaceship) and eventually thwarted of the ice.
The scene then cuts towards Korvac who reveals his origin and his plan.
Korvac used to be a computer techno, working for the Badoons, who collapsed of sheer exertion at work. As punishment Badoons grafted his body into a giant machine making him a living computer. This made Korvac powerful enough to escape his masters. Then Korvac was pulled into contest of champion against Dr. Strange by the Grandmaster (as seen in Giant Size Defenders Vol 1 # 3). Korvac allowed Dr. Strange to beat him, and manage to siphon a portion of Grandmaster’s powers. He was, alongside everyone else, returned to his proper era by Grandmaster after the game ended, however Korvac thanks to having absorbed Grandmaster power gained a new ability, teleportation. He then created his base and collected his minions. His plan was to cause the sun to go nova so that he can absorb that energy and somehow use that to take over the galaxy.
Guardians of the Galaxy likewise figure-out that Korvac is a threat to the universe and decide to confront him, without knowing the full details of Korvac plans. Upon reaching Korvac's world they are confronted by his minions and hence Guardians of the Galaxy and Thor split up into 2 ground. Vance Astro, Yondu, Nikki, Charlie 27 and Martinex decide to confront Korvac's minion, while the 2 most powerful Thor and Starhawk decide to go after Korvac.
Thor and Starhawk arrived to fight Korvac, who teleports them outside his spaceship. Thor and Starhawk run all the way up to Korvac and get teleported again. Starhawk, noticing that Korvac is actually using a machine to teleport gets Thor to destroy it and then they go to confront Korvac a third time. Korvac first puts up a stasis field barrier which is broken by Nighthawk. Korvac then attacks them with energy beam which is absorbed by Thor hammer. Korvac then fires a neural beam from his eye socket, that forces Thor and Starhawk to fight with each other. Seeing as neither have any defense against it, they decide to actually unleash their power so that the resulting fight would destroy Korvac’s spaceship, which they do. Seeing his spaceship destroyed Korvac teleports away.
Starhawk using Korvac machines teleports Thor back into his proper time.