<P> Ronan meets with Gamora's adoptive father, Thanos, to discuss her betrayal . Quill's group flee to Knowhere, a remote criminal outpost in space built in the giant severed head of a Celestial . A drunken Drax summons Ronan while the rest of the group meet Gamora's contact, the collector Taneleer Tivan . Tivan opens the orb, revealing an Infinity Stone, an item of immeasurable power that destroys all but the most powerful beings who wield it . Tivan's tormented assistant Carina grabs the Stone, triggering an explosion that engulfs Tivan's archive . </P> <P> Ronan arrives and easily defeats Drax, while the others flee by ship, pursued by Ronan's followers and Gamora's adoptive sister Nebula . Nebula destroys Gamora's ship, leaving her floating in space, and Ronan's fighters capture the orb . Quill contacts Yondu before following Gamora into space, giving her his helmet to survive; Yondu arrives and retrieves the pair . Rocket, Drax, and Groot threaten to attack Yondu's ship to rescue them, but Quill negotiates a truce, promising the orb to Yondu . Quill's group agrees that facing Ronan means certain death, but that they cannot let him use the Infinity Stone to destroy the galaxy . On Ronan's flagship, the Dark Aster, Ronan embeds the Stone in his warhammer, taking its power for himself . He contacts Thanos, threatening to kill him after first destroying Xandar; hateful of her adoptive father, Nebula allies with Ronan . </P> <P> The Ravagers and Quill's group join with the Nova Corps to confront the Dark Aster at Xandar, with Quill's group breaching the Dark Aster with the Milano . Ronan uses his empowered warhammer to destroy the Nova Corps fleet . Gamora fights and defeats Nebula, who then escapes, but the group find themselves outmatched by Ronan's power until Rocket crashes a Ravager ship through the Dark Aster . The damaged Dark Aster crash - lands on Xandar, with Groot sacrificing himself to shield the group . Ronan emerges from the wreck and prepares to destroy Xandar, but Quill distracts him, allowing Drax and Rocket to destroy Ronan's warhammer . Quill grabs the freed Stone, and with Gamora, Drax, and Rocket sharing its burden, they use it to destroy Ronan . </P> <P> In the aftermath, Quill tricks Yondu into taking a container supposedly containing the Stone, and gives the real Stone to the Nova Corps . As the Ravagers leave Xandar, Yondu remarks that it turned out well that they did not deliver Quill to his father per their contract . Quill's group, now known as the Guardians of the Galaxy, have their criminal records expunged, and Quill learns that he is only half - human, his father being part of an ancient, unknown species . Quill finally opens the last present he received from his mother: a cassette tape filled with her favorite songs . The Guardians leave in the rebuilt Milano along with a sapling cut from Groot . </P>

Who plays who in guardians of the galaxy