The Disembodied Soul (DS) is one of Bungie's many fictional characters and inside jokes at Bungie. In any Halo 3 Postgame Carnage Report on bungie.net without screenshots, a picture of the Disembodied Soul takes the thumbnail's place.
The Disembodied Soul dates back to 1997 when it was created to explain why 1,500 Marathon Infinity CDs were colored yellow-and-black instead of the Bungie colors, a problem which Bungie team members had to rectify themselves.
DS was also blamed for the "pirate" incident where Marathon source code was leaked to the net.
Bungie later made the soul into a ban-bot, using cookies stored on a previously banned members' computer to prevent multiple spam and advertising accounts.