Does They Are Billions have multiplayer?

No. As of November 2026, They Are Billions is a single-player game on PC, Xbox and PlayStation, with its campaign and survival modes played alone, and it's a paid game. If you want its walls-against-a-horde feeling with a friend, Age of Darkness: Final Stand and Conan Unconquered both have two-player co-op.

Does Diplomacy is Not an Option have co-op?

No. Its developers have said on its Steam forums that multiplayer isn't planned, and as of November 2026 it's still single-player, with no co-op announced; recent updates brought a map editor and faction reworks instead. It's a great medieval siege game alone. For a medieval village that friends defend together, Hearthfall is the co-op alternative.

Is Hearthfall as hard as They Are Billions?

It's gentler by design. In They Are Billions one breach can end everything. In Hearthfall the Keep can take a real beating, walls can be patched mid-fight, and your people heal up at every dawn. It still bites: the monsters get tougher every day, and the Lord difficulty makes them 35% stronger.

Which co-op game has the biggest hordes?

Age of Darkness: Final Stand, built around hordes thousands strong, with two-player co-op since its 1.0 release in January 2025. Swarms on the scale of They Are Billions are its whole identity. Hearthfall's waves are much smaller, and the game spends more of its time on your village, your jobs and your heroes than on sheer numbers.

Games Like They Are Billions With Co-op (2026 Picks)

They Are Billions is a solo nightmare, and it has no co-op. If you want games like They Are Billions to survive with friends, start with Age of Darkness: Final Stand or Conan Unconquered (two players each) or The Riftbreaker (four). Hearthfall is a lighter, cosier medieval pick where four friends hold one village together in the browser.

There's nothing like watching a horde roll towards your walls, except watching it with a friend who's yelling that the east gate is open. Below are the games that keep that walls-and-waves feeling and let you share it. Facts about other games are as of November 2026, from their store listings and publishers. We make Hearthfall (the complete Hearthfall guide covers it), and we'll say plainly when something else fits you better.

Is They Are Billions multiplayer?

No. They Are Billions is a single-player steampunk colony defence game: you build a colony, wall it in and try to survive an infected horde that grows until it can swallow the whole map. It's a paid game on PC, Xbox and PlayStation (Steam), and both its campaign and survival modes are played alone.

Its closest medieval cousin, Diplomacy is Not an Option, is solo too. Its developers have said on its Steam forums that multiplayer isn't planned, and as of November 2026 none has been announced. So the real question is which games keep the spirit (an economy you build, walls you hold, a horde that won't stop) and let friends in.

The comparison table

Game	Co-op players	Setting	Platforms	Cost	Best at
Age of Darkness: Final Stand	2	Dark fantasy	PC	Paid	Huge hordes, tough survival
Conan Unconquered	2	Sword and sorcery	PC	Paid	A shared base against waves
The Riftbreaker	4 (PC)	Sci-fi	PC	Paid	Base building plus mech action
Hearthfall	1 to 4	Medieval	Browser	Early access (Pixaplay Pass)	Splitting the jobs in one village
They Are Billions	1 (no co-op)	Steampunk	PC, Xbox, PS	Paid	The original, alone
Diplomacy is Not an Option	1 (no co-op)	Medieval	PC	Paid	Medieval siege defence, alone

Age of Darkness: Final Stand: the closest match

If it's the horde itself you love, start here. Age of Darkness is a dark fantasy survival game where every "Death Night" throws a vast wave at your walls. It left early access with its 1.0 release, which added cooperative multiplayer for two players: you share blessings and trade resources while you fight elite Nightmares side by side.

Better than Hearthfall for: sheer scale and a punishing challenge. Less good for: groups of three or four, or anyone without a gaming PC.

Conan Unconquered: Petroglyph's co-op survival RTS

Conan Unconquered comes from Petroglyph, the studio of former Command & Conquer developers. It's a survival RTS built around two-player co-op, with both of you building and defending one shared base against the waves. It's a paid game on Steam, with 12 co-op missions as well as its survival maps.

Better than Hearthfall for: a classic, mouse-heavy RTS feel for two. Less good for: bigger groups, since co-op stops at two.

The Riftbreaker: four players and a mech

The Riftbreaker mixes base building, turrets and action: each player pilots a mech on an alien world while the base holds off the waves. Its free 2.0 update in August 2025 added online co-op for up to four players on PC, covering the campaign and Survival mode.

Better than Hearthfall for: four players who want 3D action and a long campaign on PC. Less good for: groups who want to command an army, or medieval walls.

Hearthfall: a cosier co-op take

Hearthfall keeps the They Are Billions shape (build an economy by day, survive the night) but swaps the endless swarm for a smaller village where each friend runs part of it. One keeps everyone fed, one trains the army, one raises the walls and towers, one scouts the wilds. Up to four of you share it, and solo you do all four jobs.

Skeletons and the Lich Sovereign attacking soldiers outside stone walls and towers at night — The waves grow every night. Upgraded stone walls and watchtowers with archers inside are what hold them.

It forgives where They Are Billions punishes. Your Keep starts at 1,500 hp and goes past 3,000 once it's fully upgraded, walls can be patched while the fight is still going, and every unit heals half its health at dawn. A breach is a scramble, not instant doom. But it still ramps up, and quickly. Here's what grows as a run goes on:

What grows	How much
The night's wave	Night 5 is about four times night 1, night 10 about eight times in the campaign
Lairs sending monsters	One on the first two nights, two on nights 3 to 5, all of them from night 6
Each monster	About 10% more health and 6% more damage every day
Your group	Four players face about 2.4 times a lone player's wave
Lord difficulty	Monsters 35% stronger, and 15% less to start with

On top of that come the night's omen and, in Endless, champion nights. The good news: every lair you destroy makes later nights 12% smaller. Instead of only holding out, the campaign sends you on the attack: break the three lairs' seals and storm a 5,000 hp Citadel. The Hearthfall campaign guide covers that siege.

Hearthfall Battering Rams, knights and footmen gathered outside the gate at dusk — In the campaign you go on the attack: the Battering Rams and their escort head out to break the lairs and storm the Citadel.

The catch: it's an early-access beta for Pixaplay Pass members, still being built, so expect changes. Play Hearthfall in your browser.

Who should play what?

You want the biggest horde and a real fight: Age of Darkness: Final Stand, two players.
You want old-school RTS with one friend: Conan Unconquered.
You're four and want action: The Riftbreaker.
You're three or four and want a medieval village with split jobs, nothing to install: Hearthfall.
You're playing alone: They Are Billions and Diplomacy is Not an Option are still the best at what they do.

If your group likes the "build, then survive the night" rhythm more than the horde, see our Thronefall-style co-op games. For more strategy picks with no PvP, try the full co-op RTS games list. And if you want waves and towers with a roguelite twist, Pixaplay's Rogue Defenders is a co-op tower defense game.

Ready to hold the walls together? Start a Hearthfall run.