Quote Originally Posted by Iscah View Post

The two methods aren't as different as you're simplifying them to be.

The Ascians' ultimate aim is destabilising the world's aether to the point that it triggers a calamity. Primals - and stoking people's fears to encourage them to summon primals - are means rather than an end goal.

Meanwhile, Black Rose is very much an aetherial weapon, not just a chemical one. It's not a poison - it kills by halting a person's life energies so they stop breathing. It shifts energies towards umbral/Light, making it a match for the First's Light-soaked state. That what made it seem ideal for Emet-Selch's plan - although in the end it sounds like it may have worked too well.
They're actually radically different. Primals rely on people to shape them, summon them, and to feed them. Faith, crystals, will to attack or defend etc. Not all primals are antithetical to the planet. Ramuh for instance is mostly content to gorge on crystals and keep to the Sylphland as a guardian.

Individual Primals of the tier that we deal with in the 2.0 MSQ aren't enough to cause a Calamity, and they all have elements that do not shift the planet's aether toward a singular aspect, since we basically rotate through the whole wheel.

Then, the primal big enough to cause Calamity, like Bahamut, strikes at the planet itself, though it may be intent on assaulting mankind.

Blackrose is a chemical weapon that directly kills the people, not the land. They bring about the 8th Calamity by killing people only. Since no one can live through exposure to this chemical, it's more deadly than any primal, and it changes the lay of the planets aether, how I wonder? What with mass death by aetherial stasis? It's Light aspect, right? I kind of don't understand how it caused damage to the planet by only killing people.