To change the difficulty setting for your server, log into Multicraft, select and stop your server and follow these steps:

1. On the left hand side of your control panel click "Config Files"
2. Choose the first file named "Server Settings"
3. Scroll down to the Difficulty field.
4. Choose the difficulty you would like for your server. This can be Peaceful, Easy, Normal, or Hard.
5. Click "Save" at the bottom.
6. Start your server.

If you're wanting your server to be a Hardcore server (When you die, you are banned from the server). Enable "Hardcore" in the Server Settings.