Sentinel Prime

Sentinel Prime is the homeworld of the Night Sentinels and their greater race, referred to as the Argenta, and is a location and the eighth level in Doom Eternal. The Gladiator is fought here as a boss.

Pre-release
Some early screenshots of Sentinel Prime showed Mars in the planet's sky, possibly indicating that it existed on Phobos or Deimos in an alternate dimension or within a different time frame. This detail seems to have been redacted in the final game and replaced by a red-colored moon, which can be seen more clearly on the game's title screen when the player's current campaign is saved on this level.