Onslaught is a powerup which occurs in Doom Eternal, taking the form of a flaming purple sphere with a skull inside. Just like the quad damage item from Doom (2016), this powerup multiplies all damage the player inflicts by four; when fired, weapons will also play a sound effect derived from Quake's quad damage item.
The powerup lasts for ten seconds once collected (with a short extension for each enemy killed), and while active the player's weapons glow purple and a purple haze appears at the corners of the HUD.
Onslaught allows even the strongest opponents, such as tyrants, to be killed with far less ammunition. Because it only lasts for ten seconds, it should be saved until it is really needed and the player knows which demons to prioritize.
In Horde Mode, if you manage to kill all the bounty demons in each Arena round quickly then the last demon will leave behind a special Onslaught powerup; this item will be either gold, silver or bronze depending on how quickly the bounty demons were killed, and in addition to granting increased damage for a short time it will multiply all points earned by four, three or two respectively.
Two normal Onslaught powerups will also appear in each Bonus Blitz round; these items respawn and are vital for killing the super-heavy demons quickly while their point values remain high.