How to Fix a Tensura Neo Otherworld Server That Keeps Crashing

1. Wrong Java version for NeoForge 1.21.1

NeoForge 1.21.1 requires Java 21. A server still set up with an older Java runtime — left over from a previous Minecraft version or a default host image — will either refuse to boot or crash during world load with little explanation in the console. This is the fastest thing to rule out before anything else, since it produces symptoms that look identical to a 'the pack is broken' crash.

• Check the Java version the server process is actually launching with, not just what's installed on the machine
• Confirm the launch script or panel points at a Java 21 binary, not a cached Java 17 or Java 8 path

2. Per-player skill and race progression tracking building up

Tensura-style packs track each player's skill acquisition and race-based progression continuously in the background, not just on demand. This is the same category of ongoing state tracking seen in other Tensura-themed packs. On a world that's been up for a while with several players online, that tracking adds a steady background cost to every tick, which can look like the server 'getting slower for no reason' rather than crashing outright.

If TPS drifts downward over hours of uptime rather than dropping suddenly, this kind of continuous per-player tracking is a more likely cause than a single bad mod.

3. Growing combat-tick cost as players get stronger

This pack scales player power significantly over time, in the classic isekai power-fantasy style. As players reach higher power tiers, the encounters they fight scale up to match — more entities, bigger abilities, more simultaneous effects resolving per tick. A server that handled early-game fights fine can start showing tick spikes or timeouts later purely because the combat load itself has grown, not because anything is misconfigured.

Worth checking whether crashes or freezes cluster around specific players' late-game fights rather than happening randomly — that pattern points at scaling combat cost rather than a stability bug.

4. Corrupted per-player progression data (usually about a specific mod conflict or config corruption)

Because skill and race progression is saved per player, a bad shutdown — a crash, a forced stop, or a power loss mid-save — can leave one player's progression data in a half-written state. On the next boot, the server can hang or crash specifically while loading that player's data, which looks like a whole-server crash but is actually scoped to one corrupted file. If the server reliably crashes on boot after a hard stop but was fine before, check whether removing or restoring just that player's saved data lets the rest of the world load normally.

5. RAM under the pack's realistic floor

8 GB is the real floor for Tensura Neo Otherworld. Below that, the server usually doesn't crash cleanly the moment it runs out of headroom — it shows up first as cascading lag and longer garbage-collection pauses as the ongoing skill/race tracking and scaling combat load compete for memory, and only turns into an actual tick timeout or crash once that pressure has been building for a while. If crashes get worse the longer the server has been up and the more players are on, check RAM headroom before assuming it's a mod problem.