Steps to Reproduce

1. Open Minecraft Server; Join
2. Enter a dungeon with custom mob spawner from "Dungeons Arise"
3. Within a minute or two, an entity will spawn causing the crash

Description: Ticking entity

java.lang.IllegalStateException: Unregistered holder in ResourceKey[minecraft:root / minecraft:mob_effect]: minecraft:mob_effect@magistuarmory:laceration
at MC-BOOTSTRAP/[email protected]/com.mojang.serialization.DataResult$Error.getOrThrow(DataResult.java:287) ~[datafixerupper-8.0.16.jar%23102!/:?] {re:mixin}
at MC-BOOTSTRAP/[email protected]/com.mojang.serialization.DataResult.getOrThrow(DataResult.java:81) ~[datafixerupper-8.0.16.jar%23102!/:?] {re:mixin}
at TRANSFORMER/[email protected]/net.minecraft.world.effect.MobEffectInstance.save(MobEffectInstance.java:318) ~[server-1.21.1-20240808.144430-srg.jar%23226!/:?]

Expected Behavior

No Crash

Actual Behavior

Server crashing

Your Minecraft version

1.21.1

Your error log

https://gist.github.com/rx88xr/69a1661560e8b23d22a815d03a699551

Additional Comments

No response

Conclusion

• I agree that I am inattentively reading the description, just filling out everything