Base information

• Minecraft version: 1.12.2
• Mod version: lastest
• Minecraft Forge version:
• Mod Pack: Chroma technology 1.3.1

There is no crash but i've spawned 2 chaos guardian on my overworld with broken spawners + chaos core. 2 dragons have spawned, i killed them but they wont dispawn and i get a white screen.

Spawning boss mobs forcefully with mob spawners is not supported. There's a reason why it's disabled in the config.

I didn't change anything in the pack.

If u can't help stop comment for saying nothing.

No need to be rude, @FoxMcloud5655 is correct, Spawning boss mobs are disabled by default in the config, either the Modpack creator or yourself has changed the config.

You will need to kill the dragons with Console commands, and don't do that in the future.

Try this. /kill @e[type=draconicevolution:chaosguardian]
The guardian should not break like this in the overworld but something in your pack is probably breaking it. I suggest avoiding trying to spawn guardians with spawners.

I already tried to kill them by commands but nothing happens. Thooses dragons stay here like that.

You might have to use MCEdit to delete them.