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Modding Slay The Spire on Steam Deck

Mar 21, 2025/Steam Deck/Gaming, Modding, Steam Deck

Slay the Spire is an great game, but it feels much more complete with the Downfall Expansion Mod. Here’s how to get it running on your Steam Deck.

Step 1: Access the Community Workshop

Visit the Slay the Spire Community Workshop and download the Downfall mod. This will also install other required components, such as stslib and ModTheSpire.

Step 2: Configure ModTheSpire

The ModTheSpire UI is highly unstable on the Steam Deck, so it’s best to avoid interacting with it directly. Instead, you can pre-configure the mods to load automatically at startup.

  1. Navigate to the following directory on your Steam Deck:
   ~/.local/share/Steam/steamapps/compatdata/646570/pfx/drive_c/users/steamuser/AppData/Local/ModTheSpire
  • Note: 646570 is Slay the Spire’s Steam App ID. You can confirm this on SteamDB.

  1. Open the ModTheSpire.Properties file in a text editor.

  2. Add the following line to specify the mods to load:

   mods=basemod,stslib,downfall

Step 3: Launch ModTheSpire

Go back to the main Steam menu, click on Slay the Spire, and launch it. When prompted, select ModTheSpire as your default launch option.

If you are not prompted, go into the general settings of Slay the Spire and set ModTheSpire as the default launch option.