Heya,

I chucked a pied piper in an apotheosis spawner with the no AI upgrade it crashes the game (Breaking the world in the process). I have seen a similar issue before with twilight forest's swarm spiders - Shadows-of-Fire/Apotheosis#648

Are you able to investigate?

I'm running a custom modpack, here's the relevant lines from the debug log:
net.minecraft.crash.ReportedException: Ticking block entity at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:855) ~[?:?] at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:291) ~[?:?] at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:787) ~[?:?] at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:642) ~[?:?] at net.minecraft.server.MinecraftServer.func_240783_a_(MinecraftServer.java:232) ~[?:?] at java.lang.Thread.run(Unknown Source) [?:1.8.0_341] Caused by: java.lang.ClassCastException: shadows.apotheosis.spawn.spawner.LyingLevel cannot be cast to net.minecraft.world.server.ServerWorld at com.github.alexthe666.rats.server.entity.EntityIllagerPiper.canSpawnOn(EntityIllagerPiper.java:227) ~[rats:7.2.0] at net.minecraft.entity.EntitySpawnPlacementRegistry.func_223515_a(EntitySpawnPlacementRegistry.java:60) ~[?:?] at shadows.apotheosis.spawn.spawner.ApothSpawnerTile$SpawnerLogicExt.checkSpawnRules(ApothSpawnerTile.java:272) ~[apotheosis:4.8.9A0] at shadows.apotheosis.spawn.spawner.ApothSpawnerTile$SpawnerLogicExt.func_98278_g(ApothSpawnerTile.java:199) ~[apotheosis:4.8.9A0] at net.minecraft.tileentity.MobSpawnerTileEntity.func_73660_a(SourceFile:62) ~[?:?] at net.minecraft.world.World.func_217391_K(World.java:491) ~[?:?] at net.minecraft.world.server.ServerWorld.func_72835_b(ServerWorld.java:371) ~[?:?] at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:851) ~[?:?] ... 5 more

will be fixed in 1.19. This is indeed the same issue as the swarm spider one, and I went and made sure none of the other mobs also had this issue

FYI for future readers, if you experience this in 1.18 (Issue is only patched 1.19 and later), follow steps in Shadows-of-Fire/Apotheosis#669

Open forge server config ( \serverconfig\forge-server.toml)
modify or add:
removeErroringBlockEntities = false
removeErroringEntities = false