There are still no vampires coming to Vampire Survivors, but what is coming on August 17 is a new couch co-op mode that will let up to four people jump in to do battle with the game's multitudinous enemies—and, just a little bit, with each other.
Couch co-op multiplayer will be accessible in both new and ongoing games, so if you're well into it with lots of unlocked characters and levels, you can keep on rolling from there rather than having to start a new game. It will work with the base game and all DLC, and you'll also be able "seamlessly" switch between solo and co-op play between stages, and unlock all Vampire Survivors achievements in either mode.
"In short: you will be able to play the whole game in local co-op!" developer poncle said. "And yes, this will also work on Steam Deck if you sit together close enough (or connect it to a TV)."
Poncle said that "gameplay stays largely the same" in co-op mode, aside from the obvious uptick in on-screen chaos, but the XP bar will be shared and players will "level up in turns." There will be no multiplayer-specific levels or achievements, as poncle said it doesn't want anyone to feel like they have to play co-op in order to see and unlock everything in the game. Online play will not be supported but poncle said it will work just fine with systems like Steam Remote Play Together, and while there's no PvP mode, "we're sure some of you will find a way or two to test how good your friendships are in the co-op."
One thing I wonder about is how Vampire Survivors will handle four players running around on the screen at the same time: poncle said that "all players will always be visible on the same screen (so no splitscreen)" but how exactly that's going to work isn't being revealed just yet. Will players have to stick close together, or will the camera zoom way out to let them spread across the map?
The studio did confirm that all future updates and paid DLC will be fully accessible in both solo and co-op modes.
A beta for the Vampire Survivors couch co-op mode will be made available on the new-engine branch on Steam, but a specific date hasn't been announced yet. If you'd like to get in on that action, right-click Vampire Survivors in your Steam library and select "properties," then select the Betas menu, and choose "new-engine" from the beta participation dropdown.
