Ghost Master (known as Ghost Master: The Gravenville Chronicles on the Xbox.) is a puzzle/strategy game for the PC. It is among a small selection of games that put the player in the role of the enemy. In this case, the player assumes the role of a Ghost Master, a bureaucratic spirit tasked to perform certain duties. While the bulk of a Ghost Master's duties consist of hauntings, a Ghost Master may also be "called in" to increase belief in the supernatural, avenge deaths, and conscript renegade ghosts. Because a Ghost Master cannot directly interfere in the world of mortals, he is given a team of subordinate ghosts to do so. When not haunting, the Ghost Master is responsible for the training of the ghosts under his command.
The game was later published on Mac OS X by Feral Interactive.
Source: Wikipedia, "Ghost Master", available under the CC-BY-SA License.