I tried to use the Amthirmis Staff in a skeleton mob then immediately the server crashed and I literally cannot play anymore because the server is not even being able to start (it's automatically crashing after I try to turn on again, even if I try to delete the mod from the server) and I don't have any backup.
I saw in the crash report log and the it's returning this error:
java.lang.NullPointerException: Cannot invoke "net.minecraft.world.damagesource.DamageSource.m_269533_(net.minecraft.tags.TagKey)" because "p_20122_" is null

I also attached the crash report file here.
The minecraft version I'm using is 1.19.4.

crash-2023-05-16_14.29.06-server.txt

that refers to this line.
https://github.com/DivineRPG/DivineRPG/blob/1.19.4/src/main/java/divinerpg/entities/projectile/EntityBouncingProjectile.java#LL42C59-L42C59
Thanks for the report

This was fixed in 8536bf4 but it is not released yet