Crash report
https://pastebin.com/Up391ntg

Nothing more to add, worked in single player, crash on load on Ubuntu Dedicated Server

I think i found the little error, i just have to move a line of code to be executed only on Client. Will fix on next release, i just have to make sure another thing is working, it won't take much. I'm sorry but i can't easily test what happens in servers so thanks for reporting it.

Everything should be fine in the next release, just wait a few days and i'll upload it on curse.

While I have you there, do you think it coulld be possible to add Druidcraft SoulFire to the Heat Source like you did the Malum's Ether?

EDIT: When you have the next version published I'll try it again on my server, and going forward, so you'll have a tester for that now lol (if only for the Urn and additional heat source, this mod MUST be in my custom pack XD)

Sure it's pretty easy to do (even if it totally conflict if another mod do what i'm doing but there isn't another way right now).

I also found the way to quick test servers, so i can at least prevent dumb errors like this one :P .

That said, i should upload the update smth around tomorrow or the day after. Note : Curse may take care of it but know that it will require GeckoLib and probably Forge updated to 36.2.
I'll need a short break after that, the new fella took a lot of energy to make and i bet it's still not perfect.
Thanks for support.

Uploaded, beta 7b should work as intended.