Quote Originally Posted by SKgaming View Post
Ok thanks for this.

But what elemental unbalance would have occurred in the first if the Warriors of Light had indeed killed Cylva (The Shadowkeeper)? Would it have been a Shadow Calamity on the source then?

Is it that the timeline where the black plague was unleashed on the Source the result of Cylva actually dying? and the current timeline is one where she lived, hence avoiding the calamity from occurring on the source?

Sorry I still find this all very confusing.
It's the other way around, the First was very light heavy. Killing the shadowkeeper should have resulted in too much light, which should have been the event for a light-based calamity in the Source. Eventually the First would have been consumed by the Light due to the machinations of Eulmore over the course of decades.

"Urianger finds that the Source's understanding of active aether as "astral" and static aether as "umbral" is the reverse of what the people of the First believe. As the color white is produced by the absence of other colors, the First came to call static aether "light," while the color black is produced by the absorption of all colors, so they call the active aether 'darkness'

With this new information, Urianger deduces that since the Black Rose operates by bringing its victims' aether to a standstill, it must have a strong affinity with static or "light" aether. Having uncovered the process of Umbral Calamity, Urianger explains that as the First reaches true stasis, the Flood of Light would begin leaking light aether to the Source. He concludes that in the future, the Empire's use of the Black Rose coincided with the First being completely consumed by the light and Rejoining with the Source. This unleashed a massive amount of light aether on the Source, resulting in Black Rose's unexpected potency and causing the Eighth Umbral Calamity." - https://finalfantasy.fandom.com/wiki...al_Fantasy_XIV)