Guardian (not to be mistaken with Guardian/Thor from the original Painkiller) is the first boss in Painkiller: Overdose.
Guardian is a giant stone golem that, as it's name indicates, is guarding the Black Tower - an exit route from Belial's prison. He resembles stone golems found previously in Cataclysm level both in design and abilities, the exception being it's size and damage it inflicts.
After entering the area, ground around Belial collapses, leaving him with little space to maneuver. This makes Guardian's attacks more dangerous, as they can push the player off the ledge into the abyss. Everytime the Guardian attacks, parts of it's lava-filled body overheat, turning from red to bright-yellow. This is where you should attack the monster in order to hurt it. Once you bring enough damage on the Guardian it falls apart.
- This boss looks exactly like the standard stone golems encountered throughout the game.