For some reason it crashes whenever I enter the dimension
https://paste.dimdev.org/owowowicub.mccrash

This doesn't look like an Atum crash.
Backup your world and try removing Galacticraft (and Micdoddle core).

As sscards said, this does not seem to be an issue related to Atum. Some mob is crashing when trying to get spawned, and the stack trace would've looked different if it was caused by a Atum mob due to how Atum adds mob spawning in the dimension.