Detectives have been unable to identify the victim, who is believed to have died from a suspected drugs overdose at the Swedish House Mafia concert in Phoenix Park.
Elsewhere, three of the injured men are in a serious condition in hospital after the knife attack.
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Hide AdA 23-year-old was arrested over the a number of, but not all, of the assaults.
More than 45,000 fans packed out the open air venue for the concert, which featured Snoop Dog, Tinie Tempah, and Calvin Harris.