Dorium Maldovar

Dorium Maldovar was a black marketeer in the 52nd century.

Biography
In 5145, After hearing that she was in search of time travel, Dorium met with River Song in the Maldovarium bar to offer her a Vortex manipulator that was, according to him, "Fresh off the wrist of a handsome Time Agent". As payment Song offered him a Callisto Pulse which could disarm Micro-explosives from up to 20 feet. When he enquired as to what kind of micro-explosives the pulse could disarm, she responded by saying the kind that she had just put in his wine. He was then forced to give her the Vortex Manipulator. (DW: The Pandorica Opens)

Dorium sold a Judoon's brain that contained a security protocol to a trio of Headless Monks. As his customers left he questioned their motives for kidnapping "the child" and told them not to provoke the the Doctor's anger and rage. (WC: Prequel (A Good Man Goes to War))

Dorium was one of many people who owed the Doctor a debt and was consequently summoned by the Doctor to help in the mission to rescue Amy and her baby at Demon's Run. He did not serve in a combat role but went into the station's computer and discovered the Melody Pond had 'Human plus Time Lord' DNA.

Dorium made a fatal mistake when he and the others were surrounded by the Headless Monks. He believed they were his friends and would not harm him. He approached them with open arms, but they swiftly decapitated Dorium and added him to their ranks. His headless body was subsequently killed. (DW: A Good Man Goes to War)

Behind the scenes

 * It seems likely that this (possibly a different spelling of Maldovar) is a descriptive term for an entity from the planet Maldovarium, which Dorium could be. Further, shortly prior to his death, Dorium was referred to as "Mr. Maldavar" by Vastra.