Minor Thing

So, for all we know, shadow missions might not be the only time the player enters the shadow realm.

Where did that come from? At the same logic (if I'm understanding correctly), Manus's Shop in Dunbarton could be the Shadow Realm which it is obviously not.

Manus's shop is assumed to be the same realm, but both Shadow Realm and AnotherWorld/fakeTirNaNog are a separate from, but mostly identical to Erin/realTirNaNog.

Good you understand that, so what's your point?

My point is that the zombie field may be part of the same "world" as shadow Tara.(and that bringing up the Manus thing was kinda meaningless)

Yes, we do not know if the Shadow Realm and Another World is or is not the same world, or if either are the same world as that which takes place in Vindictus. Sorry for my misunderstanding