Twin Sails Interactive and Snake Tower Games confirmed the launch date for their deck builder with a twist.
A deck builder with a twist will arrive on Steam on May 28, 2026. The deck builder was born as a game jam prototype called Fallowtide by Snake Tower Games. Now, Twin Sails Interactive is releasing it as Moonsigil Atlas.
The release date alongside a new gameplay trailer was announced a few hours ago. Also, the demo has been rebuilt and is currently available, allowing players to see the final product before launch.
The game’s original concept came when Snake Tower Games created Fallowtide. In the game, there is no magic, no energy, no action points. There is only “space”. Each card (or sigil) has a size, and if you have enough space on your board, you can continue adding cards.
This design choice provides Moonsigil Atlas with a different flow than other deck builders. A good turn is not about using your limited resources efficiently to use your top three cards.
Instead, a good turn is about reading your board layout, creating spaces to add more cards, and figuring out ways to get more utility from the space you do have. Cards can affect each other in many ways. Through proximity, overlapping cards, runes placed on the card, keywords, or lasting effects.
The developer has designed all of the combat mechanics around this spatial constraint. As such, players can pursue perfect combo lines, create lasting effects spanning multiple turns, or craft an entire deck around a single highly impactful card.
This may help clarify how the system works in the new demo for people who are only aware of the project through its early game jam roots.
In addition to spatial deck building, Moonsigil Atlas uses modular deck construction. Players can modify existing cards. Change their shapes. Add runes to them. Change what keywords are active on them. And transform them throughout a run.
Therefore, in a game where the size and shape of a card affect how well it fits with the overall plan for your board, even a marginal improvement to a part of your deck can greatly impact how smoothly your build functions.
The full release of Moonsigil Atlas will feature over 250 cards, randomly generated runs, unlockables, alternate starting points, and three playable characters. Each of Feldryn, Aladara, and Tark’thal represent a distinct way of playing.
As such, a character focused on controlling board width will obviously play completely differently than a character optimized for compact engine builds, burst turn builds, or repeatable rune effects.
Players will battle against enemies in the astral realm and the three titans that can cause damage to the board itself.
Unlike traditional large health bar type bosses, the titans can create hostile areas on the board, alter the grid, and impose special conditions upon players to force adaptation.
Fans of Slay the Spire-type progression, Into the Breach-like spatial planning, or puzzle-based roguelites can easily understand why they would find Moonsigil Atlas appealing.
Moonsigil Atlas will launch on Steam on May 28, 2026. The rebuilt demo is available now and allows players to try out card modification, rune placement, and board-based combat before launching into the full version of the game. Below is the launch trailer.
