Atticus Thorn is the primary antagonist of the 2003 video game The Haunted Mansion which is based on the Disneyland ride attraction and the movie of the same name. He is the leader of an evil secret society known only as the Order of Shadows, an ancient cult obsessed with destroying all that is good and just in the world.
The Grand Master of the Order of Shadows, Atticus Thorn survived for centuries beyond his natural life by devouring the very souls he bent to his will. Over time, he grew stronger and amassed numerous cultists and evil spirits to aid him in his conquest of destroying the afterlife. The one way he could do so was obtain the Beacon of Souls, which the Brotherhood of the Soul always hid just beyond Thorn's grasp. During this time, Thorn had taken extreme steps to replenish the Order into a legion like no other.
After ages of searching, Thorn's scouts had tracked the Beacon's whereabouts to a manor located in the bayous of Louisiana. The remaining members of the Brotherhood had been using the manor as their headquarters, and had erected an aura to ward off the forces of evil. Of course, the protection wouldn't last for long, and Thorn managed to overcome the aura. Thorn attempted to turn Madame Leota, the local medium, to his side, but the Brotherhood managed to rescue her from the Order's clutches. In retaliation, Thorn snuffed out the lives of the Brotherhood members and imprisoned Leota within her own crystal ball.
With the Brotherhood members out of the picture, Thorn corrupted the ghostly inhabitants of the mansion, turning then into prisoners bound to serve his will. In a final attempt to thwart Thorn from spreading his evil, Leota had scattered the sacred Soul Gems (which empowered the Beacon) to the far corners of the mansion. Five of these were secured by friendly ghosts, while the sixth was left with the Beacon to leave it functioning (though rather weakly). But this didn't stop Thorn, and still he sought to claim the Beacon, along with the 999 souls.