History
R304 was a scrap farmer from the unnamed moon upon which Drax the Destroyer crash landed.
In order to get his ship, the Space Sucker repaired, Drax made a deal with a local bartender named Ora to look into missing supplies, parts, and people. During the investigation Drax interrogated R304, though the robot gave him very little assistance.
Shortly thereafter Drax came to find that even R304's body had been stolen by the very raiders he was seeking. Taking R304's head with him and returning to the site of his crashed ship, Drax encountered the raiders stripping his craft bare.
The robot reminded Drax to leave one alive, and the Destroyer then hurled R304's head at the fleeing thieves, knocking one of them down so that it could be captured and forced to lead Drax to their hideout; meanwhile, R304's head landed near the Space Sucker and was left behind without a second thought.[1]
Upon discovering that the raiders were enslaving locals on behalf of Fin Fang Foom, Drax, along with Terrax and Torgo, chased the Makluan, as well as some alien children he'd taken hostage, into the depths of the cavern. There he escaped through a gigantic portal which had been constructed from all the stolen technology.
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Drax recovering R304 from Fin Fang Foom's portal.
Serendipitously R304's head had been taken and integrated into the device, allowing him to inform the trio that the gateway led to Maklu-IV. Drax offered to free R304 from the contraption, but the robot warned that removing him, or any other component, would cause the portal to cease to function, stranding the kidnapped children. Leaving R304 there, the group traveled to confront the serpent.
Following the rescue of the slaves, Drax and Torgo subsequently returned to the unnamed moon, though Terrax chose to remain behind on Fin Fang Foom's homeworld. Drax then took R304's head with him, disabling the gateway.[2]
While returning the freed slave children to their homeworlds, Ora advised Drax to give up his vendetta to kill Thanos. R304 suggested that he listen to her before he someday accomplished his goal only to realize he'd squandered his life in doing so.[3]