>>543915621
>>543915920
It's something akin to Lovecraftian mechanics of the Dream Self. When you dream you are actually visiting another world. People can be figments of dreams of other beings and vice versa. And while this sometimes means dying in the dream doesn't affect you, other times it does.
It seems the mechanism we use runs on it and the Life Core works as an optional failsafe. If you die it can restore your record. The issue in prologue was that Renoa transplanted her Life Core into the Captain. So the Renoa in the Chaos was in real life danger.
I cannot fully discern if you are going in full body and the life core just restores us back to base, or our bodies keep being on the ship and whatever happens in the Chaos has a direct feedback. The prologue indicated the former to an extent, but Beryl's team in Chapter 2 reinforce the latter.