Helltime power is the first powerup gained for the Doom 3: Resurrection of Evil's Artifact. It is gained by killing the Helltime Hunter.
Helltime is comparable to such abilities as Max Payne's "bullet time", albeit much more advanced. When activated, time slows to a crawl around the player who continues to move quickly.
It is necessary to beat two puzzles—a room full of crusher walls and a pathway blocked by fast-moving blades. It is also necessary to beat the Berserk Hunter which moves fast.
In Helltime, the player can also out-maneuver monsters, often killing them before they have a chance to strike. Combined with the Berserk punch strength, it can be used to kill many monsters in a hurry.