Souls

This deals with the Poultry SMP multiverse

Souls are what defines a person as a person, if you have a soul then you are able to make impactful choices within your universe.

a being with a soul’s choices are what creates timelines in its home universe, if someone were to travel into the multiverse their choices would not count towards any timelines in those realities as it is not their universe of origin (or UO).