The Guardians of the Galaxy is a group consisting of Gamora, Nebula, Peter Quill(Starlord), Rocket The Raccoon, Groot, Drax The Destroyer, and Mantis. The original group was Nebula, Peter Quill(Starlord), Rocket The Raccoon, Groot, and Drax The Destoryer. They all met when they were trying to steal the power stone. They were all arrested and plotted a plan to escape together. Since they wanted the power stone, they had to prevent Ronan The Accuser from getting it. Nebula who is Gamora's sister later joined in 'Guardians of the Galaxy Vol. 2' along with Mantis. The reason why Nebula joined was because after being compared to Gamora by Thanos all the time, she wanted to kill Gamora for betraying Thanos. Gamora and Nebula settled their differences and became true sisters. Mantis joined the group after helping save the universe from Ego. Mantis was Ego's assistant until she found out his true intentions and decided to join the Guardians of the Galaxy.