A potential connection between the fate of the First and the Source?

[Enkidoh]

Also, Zenos never got his body back in the original '8th Calamity' timeline - the WoL didn't just defeat Elidibus in Zenos' body, they physically killed the body so Zenos's soul (who was getting around still in the body of a fallen Ala Mhigan Resistance fighter) never was able to reclaim it like he did in the 'changed' timeline. And presumedly also perished when Black Rose was unleashed.

This is why Black Rose was used, because 'Zenos' (or rather Elidibus) had visibly fallen at Gymlht, the Garlean troops became demoralized and withdrew and so, little by little the fired up Alliance forces pursued them into Garlemald itself, which is when Varis panicked and everything went to hell.

This is also incidentally what the ShB opening movie is actually portraying at the beginning - the WoL's fight with Elidibus in Zenos's body at Gymlht, but how it originally played out in the 8th Calamity timeline (and ended with Elidibus's defeat), not how it actually occurred for the player at the end of patch 4.55.