DaemonUmbra

Decocraft2 needs PTRLib to work (and this has not been indicated properly in the mod's code so Forge doesn't catch it) I have mentioned this on the mod's issue tracker and gotten no response. https://minecraft.curseforge.com/projects/decocraft2/issues/1673 Evidently they don't use the issue tracker, I brought this to their attention in the Decocraft2 Discord and have been told that it should be fixed in the next release.

I'm not the most experienced person here but are we sure we have enough memory free for what we're trying to give Java?

Even 1.8 won't get you support, use 1.10+

Update to a modern version to receive support.

I'm afraid your hardware may not be up to the task of running a pack this large.

All I can suggest is try to slim the pack down in items and blocks so you don’t need to use NotEnoughIDs

Your resource pack appears to have textures too small for your mipmap setting.

Please post your debug.log as described in my signature below.

I would need the log to help with that, though errors in the stackmap usually indicate a coremod is the issue (combined with the fact that it is happening in the middle of / after the handshake, I immediately suspect NotEnoughIDs as the culprit. Are you using a pre-made pack or is it your own pack?

It's complaining about your client config, not server

.minecraft/config/CustomSpawner/bophell/Creatures/ATOMICSTRYKER.cfg

It's the CustomSpawner one

NotEnoughIDs has issues in the back end, sadly it looks like you need to have it though. Try copying the configs from your client to the server.

Where did you find the jar file and what was its name?

Your atomicstryker.cfg appears to have an unrecognized character at line one, stopping it from reading properly. I also see a network issue with mo'Creatures, I would suggest updating it.

Make sure all mod configs are the same between the server and client. If that doesn't work then try removing NotEnoughIDs.

Did you build your mod using your IDE or did you use Gradle (or your IDE's Gradle Integration)?

Did you run the setupForge task?

How are you building your mod?

This log is incomplete, I need one where the issue occured, preferably one that ends in Minecraft either shutting down properly or crashing.

Please post logs as described in my signature below.

From this section of the document:

Can you provide the client's debug.log as well please? and yes you appear to have done the gist correctly.

By default Forge generates a [modid]-[version].jar and a [modid]-[version]-sources.jar. The first one is the one that is used when playing the mod, the second one is used as a library in dev environments to create addons for the mod. The way this works is your mod is not obfuscated, but every call back to vanilla minecraft is replaced with a searge mapping that stands between obfuscated and unobfuscated(MCP Mapping). To provide any further assistance I'll need logs as described in my signature below.

None of the files you uploaded worked, please post logs from both the server and client as described in my signature below.