A Journey to the Underworld: Inside the Launch of 33 Immortals

When it was first revealed at the Xbox Games Showcase in 2023, the co-op action roguelike 33 Immortals was cheered by players as a fresh new take on the tried-and-true roguelike formula. In addition to letting 33 players cooperatively battle their way through dungeons together, developer Thunder Lotus Games brought together a wide variety of gameplay mechanics (all wrapped in gorgeous, hand-drawn visuals) to create something wholly unique. Clearly that gamble has paid off in a big way, as the studio recently announced that over 500,000 players have journeyed into Inferno in Xbox Game Preview, with more joining them every day.

In honor of 33 Immortals hitting that lofty milestone, we thought it was a good time to take a closer look at just how 33 Immortals got there and what the team learned along the way. We had a chance to sit down with Creative Director Stéphan Logier, Community Manager Alison Auzias, and Director of Programming Daniel Dupuis to learn more about how Thunder Lotus brought this innovative game to life.

Microsoft Game Dev: 33 Immortals has already reached more than 500,000 players. Did you anticipate this level of success so quickly?

Stéphan Logier, Creative Director: We were hopeful that 33 Immortals would resonate with players but attracting more than 500,000 players in a couple of weeks was a wonderful surprise. The enthusiastic response from the community has been incredibly gratifying and motivates us to continue enhancing the game.

Microsoft Game Dev: Have you noticed any particular trends in how players engage with the game? Are there emergent behaviors in large-scale co-op that surprised you?

Alison Auzias, Community Manager: From the very beginning, our goal with 33 Immortals was to foster cooperation—and we’re thrilled to see players embracing that vision. It’s been amazing to watch veteran players, many of whom joined us during earlier playtests, actively helping newcomers—whether through emotes, in-game guidance, or teamwork on objectives. Their support is boosting everyone’s chances of survival and success across the board.

Microsoft Game Dev: The Game Preview release phase has provided you with a direct feedback loop with players. What have been your biggest takeaways so far, and how have those takeaways influenced development? Have there been any major design changes (or even balancing shifts) based on early player feedback?

Alison Auzias: Players have been incredibly generous with their feedback, helping us identify key areas where the game can improve. One major upcoming change centers around Inferno’s boss, Lucifer. Many players mentioned that the fight felt too easy, so we’re exploring ways to make the encounter more engaging and rewarding—while still keeping it approachable for newcomers.

Accessibility is another important focus. We’ve received a lot of input about control schemes and button mashing, and we’re actively working on improvements that will be rolled out in a future patch. 

Another thing worth mentioning is that players have really embraced the variety of cosmetics available! We’re excited to explore new ways of expanding on that in fun and engaging ways.

Our goal with 33 Immortals is to build it alongside the community, and we firmly believe that player feedback will continue to shape the future of the game.

Microsoft Game Dev: Running stable servers for a 33-player dungeon crawler is no small achievement. What were the most significant technical challenges in terms of making a co-op game at this scale feel smooth and responsive?

Daniel Dupuis, Director of Programming: The brunt of our efforts went into optimizing the game logic, which went hand in hand with our objective to keep the gameplay readable. How many players and monsters can be on screen at the same time? What are the worst-case scenarios? What about VFX? Iterating amongst ourselves and with the community helped us refine what is best for fun and performance.

Microsoft Game Dev: Have there been any surprising stress points in the server infrastructure as the player base has grown?

Daniel Dupuis: On the server side, we chose to ally ourselves with a trusted technology partner (shout out to Photon Quantum!) to help reduce risks that are hard to manage for smaller independent studios like ours. The technology has been super flexible to seamlessly scale the servers to handle increasing traffic. This allowed us to keep most of our focus on just making the gameplay as great as it can be.

Microsoft Game Dev: What’s been the most challenging aspect of matchmaking at this scale?

Stéphan Logier: Designing a matchmaking system for 33 players while preserving the surprise element inherent to roguelikes has been a unique challenge. We aim to keep each session unpredictable; this is something that we want to fine-tune during live operations, balancing the need for coordination with the excitement of unpredictability. 

Microsoft Game Dev: I’ve read that the 33 player count was chosen because each part of The Divine Comedy has 33 chapters (though Inferno has 34 to get to that nice round 100). Were there game balancing and/or server-related reasons that factored into this number as well?

Stéphan Logier: This number (33) originally comes from the Divine Comedy. The Divine Comedy has 100 chapters; each section has 33 chapters, with Inferno being slightly longer. We thought, 'OK, 33, it’s an interesting number'. We started exploring the idea of making a 2D multiplayer game by looking at how many players could fit on one screen during exploration and massive boss fights. We tried several numbers and settled on 33 because this number of players can be displayed on the screen: the game stays legible, and it looks good. So, from a gameplay perspective, 33 players is really interesting—and from a Divine Comedy perspective, it completely fits!

Microsoft Game Dev: Along these lines, have there been discussions about expanding the player count further, or experimenting with different group sizes?

Stéphan Logier: While the idea of varying player counts is intriguing, we've found that 33 players strike the optimal balance for our gameplay experience. Increasing the number could lead to overcrowded screens and chaotic gameplay, while fewer players might not capture the epic scale we envisioned. That said, we're always open to community feedback and may explore different modes or events in the future that experiment with group sizes.

Microsoft Game Dev: Large-scale co-op games often struggle with keeping all of their players meaningfully engaged. How does the game’s design work to ensure everyone has a meaningful role? What are the main methods you use to prevent the experience from being too chaotic or unbalanced?

Stéphan Logier: One of the most significant challenges we faced in designing the cooperative experience for our game was creating a gradual learning curve for collaboration. Our goal was to enable players to transition smoothly from solo play to large-scale cooperation with up to 33 players. This approach allows players to progressively develop their cooperative skills rather than being overwhelmed by a steep learning curve from the start.

To address this challenge, we designed a game mode that gradually increases the need for collaboration. When players first enter Inferno, they find themselves in a vast, open level filled with various opportunities, such as wandering monsters and chests guarded by foes. As the run progresses, players must complete chambers filled with monsters. Once enough chambers are completed, ascension battles are unlocked. After triumphing in these battles, players face Lucifer. 

As players advance through the game mode, the level of difficulty and the size of the required cooperative groups increase. Initially, opportunities are designed for 1-6 players, while chambers require 4-6 players. Ascension battles demand coordination among 10-12 players, and the final boss fight against Lucifer necessitates a team of 22-33 players. This gradual progression ensures that players not only learn the mechanics of cooperation but also come to understand that teamwork is essential for success at every stage of the game.

Microsoft Game Dev: What’s next for 33 Immortals? Can players expect new content, modes, or mechanics in the near future? How do you see 33 Immortals evolving over the long term?

Alison Auzias: New content is on the way, and you can check out our development roadmap right here! While Spring will be dedicated to making sure that the game is fun, stable and engaging for the players, we're also working on adding new game modes for this Summer: private sessions will allow players to play with up to 32 friends, an ordeal system will add new difficulty levels, and new feats will be added too. Our major update will be in Fall with Paradiso, a whole new world to discover with new monsters and a challenging final boss. There's a lot to look forward to!