How to Host an RLCraft Server

What Is RLCraft?

RLCraft is one of the most punishing and popular Minecraft modpacks ever created. Built by Shivaxi, it turns Minecraft into a brutal survival RPG with over 120 mods working together. The pack runs on Minecraft 1.12.2 with Forge, and that version lock is important because it dictates everything about how you set up and run the server.

The core of RLCraft revolves around a handful of heavyweight mods. Lycanites Mobs fills every biome with aggressive, unique creatures that can one-shot unprepared players. Ice and Fire adds dragons, both fire and ice variants, that roam the skies and guard treasure-filled lairs. Tough As Nails introduces a temperature and thirst system, so players need to manage hydration and avoid freezing or overheating. Baubles and quality-of-life mods like Carry On round out the experience.

Because of the sheer number of entities spawning at any given time and the complexity of the mob AI, RLCraft is one of the more resource-hungry 1.12.2 packs. If you underprovision your server, you will notice it immediately in the form of TPS drops and rubber-banding.

Server Requirements

Forge and Minecraft Version

RLCraft is locked to Minecraft 1.12.2 and requires Forge. The specific Forge build matters, the RLCraft server pack on CurseForge includes a recommended Forge version in its documentation. As of the latest RLCraft release (2.9.3), the recommended Forge build is 14.23.5.2860. Using a newer or older Forge build can cause mod incompatibilities or crashes on startup.

Java Version

Minecraft 1.12.2 requires Java 8. Do not attempt to run RLCraft on Java 17 or Java 21, Forge for 1.12.2 was never updated for modern Java runtimes and you will get immediate crashes related to class loading and reflection. If your host provides a Java version selector in the panel, set it to Java 8 (or OpenJDK 8). On a self-managed VPS, install openjdk-8-jre-headless on Debian/Ubuntu or the equivalent for your distribution.

RAM Allocation

RLCraft needs more memory than most 1.12.2 packs because of the entity count. Here is a rough guide:

Player Count	Minimum RAM	Recommended RAM
1–5 players	6 GB	8 GB
6–10 players	8 GB	10 GB
10–20 players	10 GB	12 GB

Keep in mind that allocating too much RAM on Java 8 can backfire. The old garbage collector (CMS or G1 on Java 8) struggles with heaps above 12–14 GB, causing long pause spikes. Stick to the recommended range and tune your GC flags instead of throwing more memory at the problem. Check our JVM flags guide for specific flag recommendations, though note that 1.12.2 flags differ from the modern Aikar flags.

Downloading and Installing the Server Pack

Head to the RLCraft CurseForge page and download the server pack, not the client pack. The server pack is a separate download, it includes the Forge server jar, all mod jars pre-configured for server-side, and the necessary config files.

Once downloaded, extract the ZIP into your server directory. If you are using a hosting panel like Pterodactyl, upload the extracted files via the file manager or SFTP. The file structure should look roughly like this:

server/
├── forge-1.12.2-14.23.5.2860.jar
├── minecraft_server.1.12.2.jar
├── mods/
│   ├── lycanitesmobs-1.12.2-2.0.7.2.jar
│   ├── iceandfire-1.9.1-1.12.2.jar
│   └── ... (120+ mod jars)
├── config/
│   ├── lycanitesmobs/
│   ├── iceandfire.cfg
│   └── ...
├── server.properties
└── eula.txt

Open eula.txt and change eula=false to eula=true. Start the server using the included start script or by running:

java -Xms6G -Xmx8G -jar forge-1.12.2-14.23.5.2860.jar nogui

The first boot takes several minutes as Forge loads all 120+ mods, generates configs, and prepares the world. Do not panic if it sits on "Loading terrain" for a while.

Common Crashes and How to Fix Them

Entity Overload

This is the number one issue on RLCraft servers. Lycanites Mobs and Ice and Fire together spawn dozens of entities per chunk. When multiple players are spread across different biomes, the entity count can spike past 1,000 and the server TPS tanks below 10.

To fix this, open config/lycanitesmobs/general.cfg and look for mob spawn rate settings. Reducing the spawn weight of Lycanites creatures by 25–40% dramatically improves performance without gutting the gameplay experience. You can also reduce the despawnTime so mobs that players run past clean up faster.

Dragon Lag

Ice and Fire dragons have complex AI, they fly, path-find in 3D, breathe fire/ice, and interact with terrain. When a stage 4 or 5 dragon is active near players, the server spends a disproportionate amount of tick time on its AI. If you notice lag spikes that correlate with players exploring new terrain, dragons are likely the cause.

In config/iceandfire.cfg, you can reduce dragonGriefing to prevent terrain destruction (which causes block updates), and lower the maximum dragon spawn rate per chunk. Some admins cap dragon stage at 4 to reduce the AI complexity of the largest dragons.

Startup Crashes

If the server crashes immediately on boot, check the crash-report folder. The most common causes are:

• Wrong Java version, "Unsupported major.minor version" means you are not on Java 8.
• Missing mods, Some mods depend on library mods (like LLibrary for Ice and Fire). Make sure you uploaded the complete server pack, not just the mods folder.
• Forge version mismatch, Using a different Forge build than what the pack specifies. Use the exact version included in the server pack.

Performance Tuning

View Distance

Set view-distance=8 in server.properties. The default of 10 loads 441 chunks per player. Dropping to 8 loads 289 chunks per player, a 34% reduction in loaded chunks. For RLCraft, where every loaded chunk contains hostile entities with active AI, this has a massive effect on TPS.

Mob Caps

In server.properties, the spawn-limits section (or in bukkit.yml if using a hybrid) controls how many mobs can exist. For RLCraft, consider reducing monster cap to 50 (from the default 70) and ambient to 5. This works alongside the Lycanites config changes mentioned above.

BAM (Better Animal Models)

If you are experiencing client-side lag reports from players, the Better Animal Models mod can cause rendering issues with its custom model system. Some server admins remove this mod from both client and server to improve frame rates. It is purely cosmetic and does not affect gameplay.

JVM Flags for 1.12.2

The widely shared Aikar flags are optimized for 1.13+ servers. For 1.12.2, you want a slightly different configuration. A solid starting point:

java -Xms6G -Xmx8G -XX:+UseG1GC -XX:MaxGCPauseMillis=100
-XX:+UnlockExperimentalVMOptions -XX:G1NewSizePercent=30
-XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M
-XX:G1ReservePercent=20 -XX:InitiatingHeapOccupancyPercent=15
-jar forge-1.12.2-14.23.5.2860.jar nogui

Note the lower G1NewSizePercent and G1MaxNewSizePercent compared to modern Aikar flags, Java 8's G1 handles smaller young generation better than the aggressive sizing used on Java 17+. For a deeper dive, see our JVM flags guide.

Day-to-Day Server Administration

Running an RLCraft server means dealing with player frustration, the pack is hard by design. Set up a world border early (2,000–4,000 blocks radius is reasonable) to limit chunk generation and keep the world size manageable. Use a plugin like WorldBorder or the vanilla /worldborder command.

Back up regularly. RLCraft worlds corrupt more often than vanilla because of the number of tile entities and custom data structures stored per chunk. A daily backup script or a hosting panel that offers automatic backups is essential. If you need a general reference for server setup, our server startup guide covers the fundamentals.

Monitor your TPS with a mod like TPS Monitor or server-side with /forge tps. A healthy RLCraft server runs at 18–20 TPS. If you are consistently below 15, revisit the performance settings above or consider upgrading your plan. Astroworld Hosting offers one-click RLCraft server setup with pre-configured Java 8 and recommended RAM. For a full walkthrough on keeping tick rates stable, check our server optimization guide.

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