Ys IX: Monstrum Nox gets experimental local co-op update on Steam

NIS America has released a new update for Ys IX: Monstrum Nox on Steam, which adds an experimental co-op mode that can either be played locally or through Remote Play Together. This co-op mode is much like the one added to the Steam version of Ys VIII: Lacrimosa of Dana.

In a post on Steam, PH3 founder Peter "Durante" Thoman details the update, which also adds support for narrower aspect ratios, which will be useful for devices like the Steam Deck. Other minor fixes have also been made.

A co-op trailer and the update details can be found below. For more, you can check out our PS4 version review or PC version impressions.

It has been a while, but today we are very happy to announce a major update to Ys IX: Monstrum Nox. The most important new feature this update introduces is local co-op. Two players can join together to not only fight monsters and explore dungeons (as in Ys VIII), but also explore the city of Balduq. Beyond co-op, this update also brings support for aspect ratios narrower than 16:9 -- which is particularly useful on e.g. the Steam Deck's 16:10 screen -- and a number of more minor bug fixes which we have accumulated since the release. These will be detailed at the end of this announcement.

Local Co-op

The local co-op feature allows two players to play Ys IX together, at every point in the story where more than one character is available.

Note that there is an in-game co-op setting which you need to enable in order for co-op to be available. Once this setting is enabled, the co-op player can drop in and out of the game using the "Start" (or equivalent) button on any non-primary controller, while the "Select" button on the secondary controller toggles the player ID indicators ("P1" and "P2") on and off.


Unlike Ys VIII, where co-op was mostly limited to combat, the second player is largely equivalent to the primary player in terms of capabilities in Ys IX, including movement and combat abilities, using Monstrum Gifts, discovering and triggering landmarks, enemies and events, opening chests, picking up collectibles, and initiating dialogue. Only interacting with menus and the map is restricted to player one.

Another significant improvement over the co-op feature in Ys VIII is that character switching is implemented individually for each player: that is, if there are 3 characters in the current party, players one and two can both independently switch to the currently-unused character without affecting each other.

Of course, given the experimental nature of this feature, there are some constraints and restrictions to keep in mind:

  • You need two controllers to play in co-op (or one controller each for Steam remote play together), and it is not possible to re-bind the controls for the second player.
  • There is shared camera control, and while the co-op camera code does its best to keep both players on screen, this takes some getting used to and requires a different approach to camera control than the single-player mode.
  • The co-op mode is experimental, and in select situations sequences of specific actions could lead to a softlock (e.g. triggering some device which closes doors with the character controlled by player 2, and then logging that player out). Please keep this in mind.

We have completed 100% of the game in co-op at Nightmare difficulty during testing, and I personally think that it is an incredibly enjoyable way to experience Ys IX.

16:10 Aspect Ratio Support

Previous versions of Ys IX used letterboxing for any resolution aspect ratio narrower than 16:9. In this version, all 3D scenes render at full resolution for aspect ratios such as 16:10 (even down to 4:3). 2D elements such as the menu or map screens will still be letterboxed as, just like for ultrawide, the effort to redesign all of these to be aspect-ratio-independent is prohibitive.

Full Changelog

New Features

  • Local co-op support
  • Support for narrow aspect ratios
  • The "Equip Screen Supersampling" graphics setting now also applies to the "Ritual Relics" screen

Fixes and Improvements

  • Make sure that traps behave functionally the same at high framerates (>>60 FPS) as they do at the default framerate
  • Fix timing of fades after video playback before Grimwald battles
  • Fix spikes at Dry Moat Ruins boss not being shown with some settings
  • Fix crash on startup when no audio devices are available
  • Fix UI animation speed of Grimwald result screen at high FPS
  • Fix a long-standing bug causing NPCs to get stuck on some ceilings after wall run
  • Fix some English spelling issues

I am personally very much a fan of local co-op in games, and feel like too few RPGs in particular offer the option to play their main campaign in co-op. I hope this update brightens the day of my fellow co-op aficionados out there, as well as anyone playing on a 16:10 monitor or who is planning to get a Steam Deck of course.

- Peter "Durante" Thoman, PH3

PS: As always, you can use the "Betas" feature on Steam to revert to a previous version of the game in case something goes wrong on your system with this patch.