DOOM Eternal - The Ancient Gods, Part One Announced offers a first look at The Ancient Gods, Part One, the first single-player expansion for DOOM Eternal. This is included in the game's year one pass, which is included in the deluxe edition of the shooter sequel. Here's a first Teaser Trailer which says to expect a full trailer on August 27th. This does not yet carry a release date. Here's what they say for now:
Your victory over the hordes of Hell spared Earth from a perilous, demon-infested fate, but saving humanity has upset the delicate balance of power in the heavens. Become the DOOM Slayer once again and set things right in DOOM Eternal’s first single-player expansion, The Ancient Gods, Part One.

Travel to previously uncharted realms of the DOOM universe and confront a new challenge head-on when The Ancient Gods, Part One releases for DOOM Eternal later this year.

This DLC expansion is part of the Year One Pass, included in the DOOM Eternal Deluxe Edition and available for purchase digitally. We have more to share soon on this exciting new chapter, so keep it locked to the Slayers Club for the latest on The Ancient Gods and all things DOOM!