Entity will not spawn. Please help

[Vulcandium]

[Server thread/WARN] [minecraft/EntityType]: Exception loading entity: 
java.lang.NullPointerException: Cannot invoke "net.minecraft.world.entity.ai.attributes.AttributeSupplier.getValue(net.minecraft.world.entity.ai.attributes.Attribute)" because "this.supplier" is null
    at net.minecraft.world.entity.ai.attributes.AttributeMap.getValue(AttributeMap.java:76) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading}
    at net.minecraft.world.entity.LivingEntity.getAttributeValue(LivingEntity.java:1835) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading}
    at net.minecraft.world.entity.LivingEntity.getMaxHealth(LivingEntity.java:1656) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading}
    at net.minecraft.world.entity.LivingEntity.<init>(LivingEntity.java:235) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading}
    at net.minecraft.world.entity.Mob.<init>(Mob.java:123) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.world.entity.PathfinderMob.<init>(PathfinderMob.java:14) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading}
    at net.minecraft.world.entity.AgeableMob.<init>(AgeableMob.java:29) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading}
    at net.minecraft.world.entity.animal.Animal.<init>(Animal.java:40) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading}
    at net.vulcandium.oceanicexpansion.entity.custom.TiamatEntity.<init>(TiamatEntity.java:24) ~[%23196!/:?] {re:classloading}
    at net.minecraft.world.entity.EntityType.create(EntityType.java:525) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,xf:fml:forge:forge_method_redirector}
    at net.minecraft.world.entity.EntityType.lambda$create$4(EntityType.java:530) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,xf:fml:forge:forge_method_redirector}
    at java.util.Optional.map(Optional.java:260) ~[?:?] {}
    at net.minecraft.world.entity.EntityType.create(EntityType.java:529) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,xf:fml:forge:forge_method_redirector}
    at net.minecraft.world.entity.EntityType.loadStaticEntity(EntityType.java:607) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,xf:fml:forge:forge_method_redirector}
    at net.minecraft.world.entity.EntityType.loadEntityRecursive(EntityType.java:563) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,xf:fml:forge:forge_method_redirector}
    at net.minecraft.server.commands.SummonCommand.createEntity(SummonCommand.java:67) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,xf:fml:forge:forge_method_redirector}
    at net.minecraft.server.commands.SummonCommand.spawnEntity(SummonCommand.java:86) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,xf:fml:forge:forge_method_redirector}
    at net.minecraft.server.commands.SummonCommand.lambda$register$1(SummonCommand.java:44) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,xf:fml:forge:forge_method_redirector}
    at com.mojang.brigadier.CommandDispatcher.execute(CommandDispatcher.java:264) ~[brigadier-1.1.8.jar%23135!/:?] {}
    at net.minecraft.commands.Commands.performCommand(Commands.java:257) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading}
    at net.minecraft.server.network.ServerGamePacketListenerImpl.performChatCommand(ServerGamePacketListenerImpl.java:1246) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.server.network.ServerGamePacketListenerImpl.lambda$handleChatCommand$11(ServerGamePacketListenerImpl.java:1223) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.util.thread.BlockableEventLoop.lambda$submitAsync$0(BlockableEventLoop.java:67) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1768) ~[?:?] {}
    at net.minecraft.server.TickTask.run(TickTask.java:18) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading}
    at net.minecraft.util.thread.BlockableEventLoop.doRunTask(BlockableEventLoop.java:156) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.util.thread.ReentrantBlockableEventLoop.doRunTask(ReentrantBlockableEventLoop.java:23) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading}
    at net.minecraft.server.MinecraftServer.doRunTask(MinecraftServer.java:770) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.server.MinecraftServer.doRunTask(MinecraftServer.java:161) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.util.thread.BlockableEventLoop.pollTask(BlockableEventLoop.java:130) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.server.MinecraftServer.pollTaskInternal(MinecraftServer.java:753) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.server.MinecraftServer.pollTask(MinecraftServer.java:747) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.util.thread.BlockableEventLoop.managedBlock(BlockableEventLoop.java:139) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.server.MinecraftServer.waitUntilNextTick(MinecraftServer.java:733) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:665) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at net.minecraft.server.MinecraftServer.lambda$spin$2(MinecraftServer.java:251) ~[forge-1.20.1-47.2.19_mapped_parchment_2023.09.03-1.20.1.jar%23191!/:?] {re:classloading,pl:accesstransformer:B}
    at java.lang.Thread.run(Thread.java:840) ~[?:?] {}
[22:09:44] [Render thread/INFO] [minecraft/ChatComponent]: [System] [CHAT] Unable to summon entity

[warjort]

Put a reproducable example of your problem on github.

[Vulcandium]

https://gist.github.com/Vulcandium/16080983071c06515cf8512accbe4764

The problem is with the attribute supplier. It says that this.supplier is null???

Edited January 6 by Vulcandium

[warjort]

Quote

Put a reproducable example of your problem on github.

That means put the build of a project on github that demonstrates the issue.

Not random and incomplete code snippets out of context.

We need to see how the code fits together and maybe try it for ourselves if the problem is not obvious.

 

Anyway, If that really is all your code, you are missing the EntityAttributeCreationEvent for your mob.

https://forge.gemwire.uk/wiki/Making_Entities#Entity_Attributes

You seem to have a static method for this called setAttributes() in your code - but I guess nothing calls it?