The Hidden is a multiplayer total conversion mod for the popular Half-Life 2 computer game.
All the other players play as the IRIS, whose goal is to work as a team to hunt down the Hidden and contain it.
After the time limit hits, or either side kills the other, the round will end, and a new Hidden may be selected depending on a number of variables including who won the previous round, who dealt the most damage, etc.
As the Hidden, the player is given several extra abilities not available to the IRIS; The Hidden is nearly invisible, with only a little distortion of the background indicating his presence, sticking to walls, and the ability to detect enemies' auras from a distance.
Other abilities include pouncing and cannibalizing corpses of slain enemies to replenish health.