“The events of Battle of Gods take place several years after the titanic battle with Majin Buu, which determined the fate of the entire universe. Old Kai, Supreme Kai, and King Kai are telepathically talking about Bill’s early awakening and Goku is running with Bubbles on King Kai’s planet. Goku notices King Kai is talking about something interesting and King Kai then tells Goku about Bills, a God of Destruction tasked with maintaining balance in the universe. Goku says he wants to fight Bills, and King Kai scolds him.
In Bills’ temple, the mysterious Whis is walking slowly with a serious look. Alarm bombs explode, but Bills still does not wake up. Whis tells him to get up and he says he will sing with a microphone if Bills keeps sleeping, and Whis is terrible at singing. Bills eventually awakens from his long slumber and asks Whis whether the galactic overlord Frieza destroyed Planet Vegeta during his nap. Bills says the Saiyans and Frieza were very evil and King Vegeta was stingy. Whis tells Bills that Frieza was defeated by a Saiyan, and Bills then uses an egg to see the past battle between Goku and Frieza. Then, Whis explains about Super Saiyans and some Saiyans living on the Earth. Bills recalls the Super Saiyan God in his predictive dream and then calls the Oracle Fish. 39 years prior, the Oracle Fish foretold that a mighty opponent would appear before Bills. The Oracle Fish does not remember it, but Bills is convinced that it said so. Since he heard rumors that a Saiyan defeated Frieza, Bills tracks down this warrior, Goku. On King Kai’s planet with his ally, the mysterious Whis, Bills proceeds to challenge Goku. Ecstatic over the new challenge, Goku does not heed King Kai’s advice and battles Bills, but he is overwhelmed and defeated. Bills then departs in order to seek out more powerful adversaries on Earth.
Meanwhile, at Capsule Corporation, Bulma’s birthday party is being held and the Z Fighters are enjoying leisure activities. Piccolo sings karaoke, a drunk Gohan appears as Great Saiyaman, the Pilaf Gang appears and they have been turned into children because they gathered all the Dragon Balls themselves and wished for youth but Shenron made them a little too young, and a motorcycle policewoman comes to Capsule Corporation at one point during the party. The drunken Gohan asks Mai to shoot him, and one of the bullets hits Videl’s leg. While healing her, Dende notices that Videl is pregnant. The God of Destruction’s arrival erupts the party, and it appears that Vegeta already knows Bills. Vegeta musters all of his excitement and casts aside his pride to put the party’s unannounced attendee in a good mood, however, Mr. Buu eventually pisses off the God of Destruction.Android 18, Tien Shinhan, Piccolo, Gotenks, Gohan, Mr. Buu, and Vegeta attempt to fight him and the God of Destruction easily defeats them one after another. Meanwhile, Whis enjoys sushi in a restaurant near Capsule Corporation, not even bothering to watch the battles unfold. When the God of Destruction slaps Bulma, it angers Vegeta and gives him enough power to resist Bills. Goku even says that Vegeta’s power has surpassed his own.
Goku decides to use the Dragon Balls and ask Shenron how to reach the Super Saiyan God. He and his friends summon Shenron, and the dragon reveals that they need the power of six pure-hearted Saiyans. Goku confronts Bills again and they wage an intense battle in space, right above planet Earth. During the titanic battle, Goku transforms into a Super Saiyan God, a form beyond even Super Saiyan 3, thanks to the power of himself, Vegeta, Gohan, Trunks, Goten, and Pan (from inside her mother, as she was not born yet), fulfilling the prophecy once stated by the Oracle Fish. The form gives Goku the power to resist Bills, but he reverts back to his regular Super Saiyan form due the form’s time limit. However, he learns the form’s godlike feeling, which allows him to use Super Saiyan God’s power against Bills.
Bills wins and tries to destroy the planet, but he runs out of power. He reveals that Whis is his martial arts master and stronger than him. He also says that there are twelve universes, and the one Goku and his friends know is just one of them.” – [Source]