[Update]: Doom Eternal's Update 6.66 has added Horde Mode, new Master levels and Battlemode 2.0.

In a bit of a departure from the usual FPS game modes, Doom Eternal wanted to add the Invasion Mode as a post-launch update. This Dark Souls inspired mode would have you invade a random player's campaign and possess a powered-up version of one the demons, after which the two of you would have a brief but highly explosive duel, with the victor getting some nifty prizes out of the whole ordeal.

However, as with many other things, the pandemic has thrown a wrench into those plans. This, combined with the community's interest in the Invasion Mode waning with time, has convinced id Software to stop working on it and instead focus on a totally new single-player horde mode.

"We're confident this horde mode will offer you more of the diversity and challenge you're looking for in the game," reads the brief update. "In addition, the team continues to work on a refresh of BATTLEMODE that includes a competitive, rank-based structure, a number of gameplay and balance updates and another new map."

Personally, I think this is very much so the correct move. If Invasion Mode was present at launch it would've been highly popular since the amount of people going through the campaign would be enormous and thus guarantee constant action, but well over a year after release I highly doubt there would be enough interest to keep the game mode alive for long. A single-player Horde mode, however, is something with a lot more potential and longevity, so I'm very happy to see it in development now.

Once we get more information about the horde mode, ideally alongside a proper gameplay trailer, I'll make sure to let you know. Until then, I'll leave you with a trailer for the most recent Update 6. Enjoy!