SULFUR Together

SULFUR Together

Co-op multiplayer for SULFUR.

Language: English · Simplified Chinese · Japanese

Version 1.4.1 — Public Beta. Built for SULFUR 0.19.9; it does not run on 0.19.3 or older game builds — stay on 1.4.0 for the earlier 0.19 builds, or 1.3.1 if you are still on 0.18.x. It works, but it is still being polished. Expect bugs, back up your saves, and make sure everyone runs the same version.

English

SULFUR Together lets you play SULFUR co-op. Explore the same procedurally generated levels, fight enemies together, revive downed teammates, see each other's weapons and attacks, break objects in the world, and drop items for each other.

You connect inside the game now — there is a built-in menu for hosting and joining over Direct IP or Steam. No config-file editing.

⚠️ Public Beta notice

This is a public test build. The main loop works from start to finish, but many systems are still being optimized and there is a lot left to refine.

• Bugs, visual desyncs, and the occasional broken boss or level transition can happen.
• Back up your save files before playing.
• Every player must use the same version of SULFUR and the same version of SULFUR Together.

This release is for players who are happy to test unfinished multiplayer and report problems.

Requirements

• SULFUR (Steam)
• BepInEx 5 — installed automatically as a dependency
• SULFUR Native UI Lib 0.10.1 — installed automatically as a dependency. It powers the in-game connect menu, notifications, and translations.

You do not have to install these by hand if you use a mod manager (below).

How to install (recommended: Gale)

Gale is a free, beginner-friendly mod manager. If you have never modded a game before, use this.

• Download Gale from its official page: — open the Releases section and grab the latest installer for your system.
• Install and open Gale. When it asks which game to manage, choose SULFUR.
• Open the Browse mods tab and search for SULFUR Together.
• Click Install. Gale automatically pulls in everything it needs (BepInEx and SULFUR Native UI Lib) — you do not need to install those separately.
• Press the Launch game (modded) button inside Gale. The first launch takes a little longer while BepInEx sets itself up.
• Every player who wants to join must do the same steps and install the same version.

That's it — you're ready to host or join from inside the game.

Manual install (advanced, without a mod manager)

• Install BepInEx 5 for SULFUR.
• Download SULFUR Native UI Lib and SULFUR Together.
• Put SULFUR Together.dll, LiteNetLib.dll, and the lang folder into BepInEx/plugins/SULFUR Together, and install the UI Lib into its own BepInEx/plugins/ folder the same way.
• Launch the game.

How to connect

Co-op is hosted and joined from inside a loaded save (not from the title screen).

• Load into your game (the hub or any level).
• Open the Options menu and go to the SULFUR Together page.
• Set your Player name.
• To host: press Create game. Then either:
• Steam: press Invite Friends via Steam — no port forwarding needed; or
• Direct IP: share the LAN address shown on the page (and, over the internet, forward the UDP port or use a VPN LAN). Everyone must use the same Connection key.
• To join:
• Steam: accept the invite (it joins automatically once you load a save), or paste the host's Steam ID and press Join via Steam; or
• Direct IP: enter the host's address, port, and connection key, then press Join game.
• Use Close room (host) or Leave (client) to end the session.

Your settings save automatically as you type. Quick keys still exist: Page Down links/follows the host, Page Up unlinks and returns you to solo play.

Features

• Host-authoritative multiplayer over LiteNetLib
• Synced procedural level generation, seeds, and level transitions
• Remote players, held weapons, and player projectiles
• Enemy movement/combat sync; host-authoritative enemy damage, deaths, and ranged attacks
• Co-op downed / rev