I'm playing on Java edition 1.21. It keeps crashing from thirty seconds to a few minutes after I open the game. The exit code is 255 and the log it gave me is this: Caused by: java.lang.IllegalArgumentException: Can't find attribute mythicmetals:fire_vulnerability

This is the full thing:

Encountered an unexpected exception
net.minecraft.class_148: Ticking entity
at net.minecraft.server.MinecraftServer.method_3813(MinecraftServer.java:1025)
at net.minecraft.server.MinecraftServer.method_3748(MinecraftServer.java:912)
at net.minecraft.class_1132.method_3748(class_1132.java:114)
at net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:697)
at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:281)
at java.base/java.lang.Thread.run(Thread.java:1583)
Caused by: java.lang.IllegalArgumentException: Can't find attribute mythicmetals:fire_vulnerability
at net.minecraft.class_5132.method_26865(class_5132.java:21)
at net.minecraft.class_5132.method_26862(class_5132.java:27)
at net.minecraft.class_5131.method_26852(class_5131.java:68)
at net.minecraft.class_1309.method_45325(class_1309.java:1977)
at net.minecraft.class_1309.localvar$dce000$mythicmetals$changeFireDamage(class_1309.java:16896)
at net.minecraft.class_1309.method_5643(class_1309.java)
at net.minecraft.class_1420.method_5643(class_1420.java:225)
at net.minecraft.class_1297.method_5730(class_1297.java:605)
at net.minecraft.class_1297.method_5670(class_1297.java:545)
at net.minecraft.class_1309.method_5670(class_1309.java:406)
at net.minecraft.class_1308.method_5670(class_1308.java:302)
at net.minecraft.class_1297.method_5773(class_1297.java:487)
at net.minecraft.class_1309.method_5773(class_1309.java:2468)
at net.minecraft.class_1308.method_5773(class_1308.java:372)
at net.minecraft.class_1420.method_5773(class_1420.java:131)
at net.minecraft.class_3218.method_18762(class_3218.java:770)
at net.minecraft.class_1937.method_18472(class_1937.java:498)
at net.minecraft.class_3218.method_31420(class_3218.java:408)
at net.minecraft.class_5574.method_31791(class_5574.java:54)
at net.minecraft.class_3218.method_18765(class_3218.java:372)
at net.minecraft.server.MinecraftServer.method_3813(MinecraftServer.java:1021)
... 5 more

This might be a duplicate of #259
If not, the crash reason is likely the same

Oh. Sorry I didn't see that. Thank you for the response, I do have eternal starlight installed and it solved the issue.