That'll arrive within update 6.66, which Bethesda's dubbed as Eternal's "biggest free update yet." Having replaced the originally planned Invasion mode inspired by Dark Souls, a teaser trailer was posted on Bethesda's official YouTube channel showing Horde in action.
Doom Eternal Introduces Horde Mode In Next Week's Update
Update 6.66 also include changes to the 2v1 BATTLEMODE 2.0, bringing in a new arena and streak-based rewards. Two new Master levels are also making their way to the game. A live stream takes place tonight at October 21, at 4:30pm PT / 7:30pm ET, featuring community manager Joshua Boyle and director Hugo Martin.
Despite launching in March 2020, it's been a busy year for Doom Eternal. With both parts of The Ancient Gods DLC now released, Eternal also arrived on PS5/Xbox Series X|S, though it wasn't an entirely seamless transition for PS5 owners. We'll keep you informed with new updates, so make sure to follow us for more Doom Eternal news.