Revive is a mysterious psy technique where the recently deceased are brought back to life.
During the Shadow War, the Shadowling Queen had the ability to revive the dead. How she was able to do this is currently unknown. She would revive some her subjects after receiving petitions from the Office of the Queen's Servant.
The sum of money to revive characters varies depending on the game difficulty set (revival of 1 character costs 20 gold on Easy, 30 on Normal, 50 on Hard, and 75 on Brutal, respectively). Therefore, it is advisable to always change the difficulty to Easy before talking to Negatus.
As long as they have a body, Duvalier and Luca can revive a fallen teammate. First, Luca puts a Soul Charge into the deceased's body. Duvalier then shapes the soul charge so that it will "fit" the individual's brain.