I haven't finished Endwalkers yet, only just got done with the Zodiak trial. However one thing that confuses me:

If Fanderial was so worried about the WoL interfering in his plans, why didn't they use that soul swapping device on us and then just kill us outright?

I'm assuming that when soul swapped out of our body we could be killed permanently - both our normal body and the body in which our soul resides.

Did he even need the WoL to defeat Zodiak? Couldn't he after having taken over and had his fun causing destruction & chaos as Zodiak, just killed himself as he did after we beat him? And thus bring about the full end-of-days anyways.

So it really boild down to:

1. Did Fanderial really need the WoL?
2. If not, and was worried about the WoL, why not just soul-swap them at any time and remove them as a threat?