DaemonUmbra

Wrong thread, elienboy.

Can you please read the "Logs" section of my signature and provide the appropriate log in the appropriate manner.

Can you provide a debug.log? (More info in my signature)

I don't get this issue launching a server for that pack. Is this a new world or an old one? How did you install the server?

That looks like a 1.7.10 KCauldron server. We don't provide support for 1.7.10 or non-Forge servers.

Are your graphics drivers all up to date?

1.7.10 is no longer supported due to its age. Please update to a modern version of Minecraft to receive support.

In the future please use GitHub Gist or Pastebin to provide logs. Have you changed anything about the pack?

Optifine needs to start making itself compatible with Forge's new loading system.

Bingo, Forge for 1.12.2 only works with Java 8 due to a fundamental change in Java that occurred in Java 9 (Forge for 1.13 works in Java 8 or 10).

Can you provide a screenshot of this message from Chrome?

Could you provide your workspace as a GitHub Repo?

Can you provide a debug.log? More info in the "Logs" section of my Forum signature below.

The thing below every one of my posts is my signature, it has further details on what I've asked you to do.

Can you please read the "Logs" section of my signature and provide the appropriate log in the appropriate manner.

Could you provide a debug log?

I believe this typically indicates an issue with a coremod. Your crash log (and your debug log) should have info on what coremods are installed.

Can you please read the "Logs" section of my signature and provide the appropriate log in the appropriate manner.

All of them? The filenames of many of your mods say otherwise.

User was banned for using a cracked launcher.

I've split your reply into its own thread, please don't hijack threads. Where are you getting your mods?

Creating a new world and deleting the old one is all you can do.

Looks like your world's corrupted.

I'll need logs from both the server and the client.