Milestone

As well as achievements, Doom Eternal and its expansions include a number of in-game milestones that are awarded for completing certain feats. Completing milestones unlocks a range of rewards including avatars, icons, main menu backgrounds and alternate skins for the Doom Slayer and his weapons.

Agnostic
These milestones can be completed in any mode.

Trivia

 * The "Barrels o' Fun" milestone is probably a reference to the Doom II level of the same name.
 * The "Super Turbo Turkey Carver" milestone is named after an arcade game from Doom 3.