The Battle on Ego's Planet was a three-sided conflict between the Guardians of the Galaxy, the Sovereign, and Ego.
When Ayesha had sent her fleet of drones on the Guardians of the Galaxy team following the reason Rocket Raccoon had stolen their batteries after defeating the Abilisk, Ego appeared and destroyed the fleet while the Guardians crashed on a nearby planet.
On the planet, Ego met with the Guardians and revealed himself as Quill's father. During the meeting, Ego attempted to make Quill return to his home accompanied by Gamora and Drax while Rocket and Groot guarded on Nebula.
When Yondu Udonta and the Ravagers arrived to capture Quill and to hand him over the Sovereign after being hired by Ayesha, Nebula tricked Groot to free her, while Taserface carries out the mutiny against Yondu and executes his loyalists with the help of Nebula, who leaves to kill her sister as revenge for being installed with cybernetic and robotic body parts by their father Thanos.
Yondu, Rocket, and Groot are taken as hostages by Taserface and his men, while Drax, Quill, and Gamora meet with Mantis, Ego's assistant which he raised.
Nebula arrives on Ego's planet and attempts to kill Gamora, who survives and defeats her sister via a blaster gun, however, she is reaching to an uneasy alliance point, and the two are exploring the planet. Gamora and Nebula are discovering thousands of skeleton remains hidden inside the caves of Ego's planet, and feeling that Ego is hiding a secret from them.
While still meeting with Quill and Drax, Ego explains that he is one of the god-like Celestials, and exists in the form of the planet on which they are standing. He assumed a human guise to travel the universe and interact with other species, eventually meeting and falling in love with Quill's mother Meredith. After Meredith's death, Ego paid Yondu to collect the young Quill, but Yondu never delivered the boy, and Ego had been searching for his son ever since.