https://pastebin.com/qdmLsL8X

Crash upon joining a world

Try Neruina mod, or I remembered that Forge has a "removeErroringTileEntities" option in forge.cfg file, turn it to "true", then turn it to "false" after it worked. I'm not sure if Fabric has this option.
I can't reproduce this issue yet, so I'm not sure about whether it is fixed in the existed versions. I'll release some versions for test, and if you want to help test these versions, please give me some feedbacks. It will help a lot, thanks!

Thanks for your help!

The issue is that the mod does not check that the attacking entity is an instance of LivingEntity before casting it to that.

This can be easily fixed, by changing

if (id.equals(endMob)) {
    LivingEntity attacker = (LivingEntity) source.getAttacker();

to

if (id.equals(endMob) && source.getAttacker() instanceof LivingEntity attacker) {

Try using ends_delight-1.20.1-2.2

crash-2024-06-27_14.04.25-server.txt

Same crash like:

...cn.foggyhillside.ends_delight.item.DragonToothKnifeEvent$KnifeEvents.onAttackEndMobs(DragonToothKnifeEvent.java:17)...

Fixed in this version?

Yes