How do calamities work, again?

[ChaoticCrimson]

I'm not sure if floods in and of themselves are entirely counterproductive, but I'm sure the Ascians don't want another fiasco like the Thirteenth to occur, causing potential damage to the whole upon rejoining. I suspect this is why Elidibus sent Ardbert and his group to the Source, probably as a way to hasten the First's rejoining before things went too far by having them begin the Eighth Umbral Calamity. After all, I get the impression that Black Rose was an improvised contingency plan afterwards due to the discovery of it's increased potency due to the change in the Source's aether brought about from the trickle effect from the First. I could be off-base though, as I'm still processing all the new info we have now.

[CaesarCV]

After all, I get the impression that Black Rose was an improvised contingency plan afterwards due to the discovery of it's increased potency due to the change in the Source's aether brought about from the trickle effect from the First. I could be off-base though, as I'm still processing all the new info we have now.

This seems to be the case given the information on the Black Rose we are aware of. The Black Rose was a project conducted by a Legio XIV Scientist in Ala Migho attempting to create a powerful new weapon for the Garlean Military. As far as we know, it was just intended as a 'conventional' chemical weapon, albeit a rather devastatingly effective one given how there's still evidence of its poison decades after the testing. Gaius Van Baelsar, commander of the Legion at the time, was not fond of this weapon. He sought to conquer and convert rather than eliminate native populations. He canceled the project, and its creator went mad. However, the formula for creating it (or notes or what have you) still existed and made it to Garlemald Proper.

The timeline becomes muddied from there on in, but Solus/Emet-Selch seems to have become aware of it more recently as he explored Varis's science projects. He found it perfect for producing a Cataclysm due to its aetherial qualities, leading to the plan in Shadowbringers. In Shadowbringers Varis mentions how Solus/Emet-Selch had a way of tricking Varis into ideas that he thought were his own. His desire to rejoin the shards to 'make humanity strong enough to defeat the Ascians' and his seeming obsession with Black Rose are likely both examples of this.